Automatic Electric Dryers

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Automatic electric dryers are not complicated to repair. The more you know about

the electrical, mechanical, and operational basics of the dryer, the easier it is to solve

the problem. Some models are designed to operate on 240 volts; other models

operate on 120 volts. To dry clothing, an automatic dryer must have drum rotation

(clockwise rotation at 40 to 60 RPM), electric heat (approximately 5600 watts), and air

circulation. This chapter will provide the basic skills needed to diagnose and repair

automatic electric dryers. Figures 20-1 and 20-2 identify where some of the components are

located within the automatic electric dryer. However, this illustration is used as an example

only. The actual construction and features might vary, depending on what brand and

model you are servicing.

Principles of Operation

The clothes are placed into the dryer according to the manufacturer’s recommendation for

the proper loading of the dryer. Next, the proper cycle is selected, and the dryer start button

is pressed. The combination of the timer, the switches, thermistors, and/or the thermostats

regulates the air temperature within the drum and the duration of the drying cycle. During

the drying cycle, room air is pulled into the dryer drum from the lower rear (or sometimes

the front) of the cabinet, depending on which model the consumer owns (Figure 20-3). The

air is pulled through the heater, drum, lint screen, down through the lint chute, and through

the fan housing. It is then pushed out of the exhaust duct. The drive motor, blower wheel,

belt, and pulleys cause the drum to turn in a clockwise rotation at 40 to 60 RPM and the air

to move through the dryer. The belt wraps around the drum, motor pulley, and idler pulley.

The blower wheel is secured to one end of the drive motor shaft, or there may be a separate

motor to turn the blower wheel. As the drive motor turns, the drum rotates, moving the

clothes. At the same time, the blower wheel turns, moving the air. The heating element will

cycle on and off, according to the temperature selected.

Functions and Cycles

Electric automatic dryers use three basic functions to operate:

• Heat is supplied by a resistance-type heating element.

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Lint filter

Drum

Drop-down

door

Electronic

controls

Motor

Heater

assembly

FIGURE 20-1

The location of

components in a

typical automatic

electric dryer. The

consumer has a

choice between a

drop-down or sideopen

door.

FIGURE 20-2

Typical component

location in an electric

dryer.

Inlet safety

thermostat

High limit

thermostat

Heaters

Idler pulley

Dryer drive

motor

Blower

wheel

Outlet control

backup thermostat

Blower motor

Outlet control

thermistor

Line ilter

Blower

housing

Line fuses

Inlet control

thermistor

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• Air is drawn into the dryer. It is heated and circulated through the tumbling clothes.

Then the warm, moisture-laden air is drawn through the lint screen and is vented

through the duct system to the outside.

• Tumbling of the clothes is accomplished with a motor that drives a belt, which

rotates the drum.

The cycles of an electric automatic dryer are as follows:

• Timed dry cycle The timed dry cycle is controlled by the amount of time selected on

the timer. The temperature in the dryer is controlled by a thermostat or a thermistor,

which turns the heating element on and off throughout the timed cycle.

• Automatic dry cycle The automatic dry cycle is not controlled by the timer. This

cycle is controlled by the cycling thermostats or thermistors. Heat is supplied to dry

the clothes, and it will continue until the temperature in the drum reaches the selected

cutout setting of the thermostat or thermistor. When the thermostat or thermistor is

satisfied, the heater shuts off and the timer motor is activated. However, certain

variables can control the cycle, which will cause the cycling of the thermostat or

thermistor before the end of the cycle.

• Permanent press and knit cycles The permanent press and knit cycles are controlled

by the amount of time selected on the timer. The temperatures of these cycles are

controlled by the temperature rating of the cycling thermostats or by the thermistors

that are located within the cabinet, on the exhaust duct, and in the air supply. On

some models, the user can select the desired type of heat setting with the temperature

selector switch, located on the control panel.

• Air dry The air dry cycle is controlled by the amount of time selected on the timer.

This cycle uses the air to dry the clothes. The heating element is not used at all

during this cycle.

FIGURE 20-3

Typical air low pattern

in an automatic

electric dryer.

Drum felt

Electric Dryer

Trap duct seal Exhaust air

Inlet air

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Safety First

Any person who cannot use basic tools or follow written instructions should not attempt to

install, maintain, or repair any automatic dryers. Any improper installation, preventive

maintenance, or repairs could create a risk of personal injury or property damage.

If you do not fully understand the installation, preventive maintenance, or repair

procedures in this chapter, or if you doubt your ability to complete the task on the automatic

dryer, please call your service manager.

The following precautions should also be followed:

• Never bypass (or interfere with) the operation of any switch, component, or feature.

• The dryer exhaust should be vented properly. Never exhaust the dryer into a chimney,

a common duct, an attic, or a crawl space.

• Be careful of sharp edges when working on the dryer.

• The dryer produces combustible lint, and the area should be kept clean.

• Never remove any ground wires from the dryer or the third (grounding) prong

from the service cord.

• Never use an extension cord to operate a dryer.

• The wiring used in dryers is made with a special heat-resistant insulation. Never

substitute it with ordinary wire.

Before continuing, take a moment to refresh your memory of the safety procedures in

Chapter 2.

Automatic Electric Dryers in General

Much of the troubleshooting information in this chapter covers automatic electric dryers in

general, rather than specific models, in order to present a broad overview of service techniques.

The illustrations that are used in this chapter are for demonstration purposes only to clarify the

description of how to service dryers. They in no way reflect upon a particular brand’s reliability.

Electrical Requirements

Electrical dryers can be connected to an electrical power source in three ways:

• Electrical cord and plug, which plugs into a 240-volt wall receptacle.

• Directly wired to a fused electrical disconnect box with a built-in shut-off switch.

• Directly wired to a circuit breaker or to a fuse panel. All dryers must be properly

wired, grounded, and polarized, according to the manufacturer’s installation

instructions and per all local codes and ordinances.

Electrical Plug Connection – Three-Wire Cord

Always install a UL-approved, 30-amp. power cord, NEMA 10-30–type SRDT with a strain

relief on the dryer electrical terminal block located in the rear of the dryer (Figures 20-4

and 20-5). You must follow the manufacturer’s installation instructions for installing a

power cord on the dryer properly.

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Electrical Plug Connection – Four-Wire Cord

The new power cord is a UL-approved, 30-amp, power cord, NEMA 14-30–type ST or SRDT

(Figures 20-6 and 20-7). The plug end is a four-prong plug. This new type of power cord

will better protect the dryer and the consumer from electrical mishaps. You must follow the

manufacturer’s installation instructions for installing a power cord on the dryer properly.

You will need an electrician to replace the old three-prong receptacle with a new four-prong

receptacle.

Electrical Tests for Electric Dryers

While performing a service call on an electric dryer, the following electrical tests should

be performed:

• Continuity Use your multimeter and set it on the ohms scale. When measuring

resistance between the terminal block ground and any exposed unpainted metal

cabinet component, including control shafts and switches, there should be no more

than .1 ohms resistance reading.

30-Amp

NEMA 10-30 Neutral

(center wire)

Access cover

screw

Terminal

block

Line 2

Brass terminal

Line 1

Brass terminal

Internal ground

green screw

Install

UL-approved

strain relief here

Terminal screw

recovery slot

Neutral

silver terminal

FIGURE 20-4

Attach the three-wire

power cord to the two

brass and silver

terminals as shown in

the igure.

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Do not remove

internal ground in

a 3-wire system

Neutral terminal

FIGURE 20-5

A properly attached

three-wire power cord.

FIGURE 20-6

Attach the four-wire

power cord to the two

brass and silver

terminals as shown in

the igure. Attach the

green wire to the

cabinet.

30-Amp

NEMA 14-30

Neutral

White wire

Ground

Green

wire

Access cover

screw

Terminal

block

Line 2

brass terminal

Line 1

brass terminal

Internal ground

green screw

Install

UL-approved

strain relief here

Terminal screw

recovery slot

Neutral

silver terminal

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• Motor power Perform an audit on the motor (power required after 20 seconds

with no load, and the motor is turning in the clockwise direction, and the electric

heater is turned off). The reading should be between 200 and 280 watts. Next, perform

a line test (power required after 1 to 5 seconds with no clothes in the dryer, the motor

is turning in a clockwise direction, and the electric heater is turned off). The reading

should be between 210 and 290 watts. If you do not have a wattmeter, use the Ohm’s

Law formula to convert to watts.

• Low voltage start The minimum voltage needed to start the dryer motor is 100 VAC,

60 Hz (200 volts for 230 VAC, 50 Hz dryers). Place about 25 pounds of clothing with

100 percent moisture into the dryer and set the dryer at its maximum heat setting.

Turn on the dryer and measure the voltage at the start of the dryer cycle. The voltage

should not be below the listed voltage for any part of the cycle.

• Drum temperatures The following test will be run with the exhaust duct vent

disconnected from the dryer. Take your multimeter temperature thermal couple and

place it in the lint grill about 1 to 2 inches. You will need to set the dryer timer as

needed for this test. The recordable temperature is to be the maximum temperature

reading after the third cycle when the heater cycles off. There should not be any

clothes in the dryer for this test. Each time the thermostat or thermistor cycles open,

there should be equal to or higher than opening temperature for the next lower

temperature setting.

• Maximum heating temperature when the heater cycles off is 120 to 160 degrees

Fahrenheit.

FIGURE 20-7

A properly attached

four-wire power cord.

Move internal ground (black)

wire to neutral (silver)

terminal for 4-wire system

Neutral terminal

Neutral

white wire

Green

ground screw

Green

ground wire

Black or red

power wire

Black or red

power wire

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• Medium heating temperature when the heater cycles off is 110 to 140 degrees

Fahrenheit.

• Low heating temperature when the heater cycles off is 95 to 130 degrees Fahrenheit.

Location and Installation of Dryer

The following are some general principles that should be followed when installing a dryer:

• Locate the dryer where there is easy access to existing electrical lines.

• Be sure that you observe all local codes and ordinances for the electrical, plumbing,

and venting connections.

• The dryer should be installed and leveled on a firm floor to minimize vibration

during operation.

• To reduce the risk of fire, never install a dryer on any type of carpeting.

• For proper operation of the dryer, be sure that there is adequate make-up (new,

replacement) air in the room where it is installed.

• Do not install a dryer in an area where the make-up air is below 45 degrees

Fahrenheit. This will greatly reduce the drying efficiency and increase the cost of

operating the dryer.

• Always follow the installation instructions that are provided with every automatic

dryer purchased. If the installation instructions are not available, order a copy from

the manufacturer.

• When installing a dryer in a mobile home, the dryer must have an outside exhaust.

If the dryer exhaust goes through the floor, and the area under the mobile home is

enclosed, the exhaust must terminate outside of the enclosed area.

• If the dryer is to be installed in a recessed area or closet area, follow the

manufacturer’s recommendation for its installation.

• When relocating the dryer to a new location, test the voltage at the new location,

and be sure that it matches the dryer voltage specifications as listed on the

nameplate (serial plate). Also inspect the entire vent system for any obstructions.

Proper Exhausting of the Dryer

Proper exhausting instructions for the model being installed are available through the

manufacturer. Each manufacturer has its own specifications for the size and the length of

the ductwork needed to run its dryer properly. The maximum length of the exhaust system

depends upon the type of duct, the number of elbows, and the type of exhaust hood used.

Figure 20-8 illustrates a typical dryer exhaust installation.

The following guide is recommended for the exhausting of a dryer:

• Keep the duct length as short as possible.

• Keep the number of elbows to a minimum to minimize the air resistance.

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• Never reduce the diameter of round ductwork below 4 inches.

• Install all exhaust hoods at least 12 inches above ground level.

• The exhaust duct and exhaust hood should be inspected periodically and cleaned,

if necessary.

• All duct joints should be taped. Never use screws to join the duct joints together.

Screws protruding into the duct will cause lint buildup, and this will eventually

clog the duct.

• Never exhaust the dryer into any wall, ceiling, attic, or under a building.

• Accumulated lint could become a fire hazard, and moisture could cause damage.

• If the exhaust duct is adjacent to an air conditioning duct, the exhaust duct must be

insulated to prevent moisture buildup.

Exhaust Ducting

The more that the dryer is used, the more frequently the exhaust ducts and vent hood must

be inspected to prevent duct blockages and lint fires. The exhaust ducting and vent hood

must be cleaned at least once a year for peak performance in drying.

When installing ductwork, separate all turns by at least 4 feet of straight duct, including

the distance between the last turn and the dampened wall hood. If a turn is 45º or less, it can

be ignored in figuring out duct distance. If you have two 45º turns, count it as one 90º turn.

Also, each turn over 45º should be counted as one 90º turn (Figures 20-9, 20-10, 20-11, 20-12,

and 20-13.

Metal duct

Dryer 2 Turns

Exhaust hood

FIGURE 20-8

Typical dryer exhaust

installation.

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Recommended

No. of 90°

Elbows

Rigid

metal

Flexible

metal

2–1/2"

4" Dia.

Rigid

metal

45 Feet

35 Feet

25 Feet

15 Feet

30 Feet

20 Feet

10 Feet

Flexible

metal

15 Feet

10 Feet

30 Feet

20 Feet

10 Feet

Use only for short

run installations

Exhaust hood types

FIGURE 20-9 Recommended maximum length

Recommended

maximum length

exhaust duct and

hood for a direct drive

blower in a dryer (one

drive motor).

FIGURE 20-10

Recommended

maximum length rigid

exhaust duct and

hood for a dryer with a

separate drive motor

for the blower

assembly.

FIGURE 20-11

Recommended

maximum length for

lexible metal exhaust

duct for a dryer with a

separate drive motor

for the blower

assembly.

4" (10.2cm) Louvered

60' (18.28 m)

52' (15.84 m)

44' (13.41 m)

32' (9.75 m)

28' (8.53 m)

48' (14.63 m)

40' (12.19 m)

32' (9.75 m)

24' (7.31 m)

16' (4.87 m)

Preferred vent hood type

Maximum Length of 4" (10.2 cm) Dia. Rigid Metal Duct

(10.2 cm)

Number

90° turns 2.5"

(6,35

cm)

4" (10.2 cm) Louvered

30' (9.14 m)

22' (6.71 m)

14' (4.27 m)

18' (5.49 m)

14' (4.27 m)

10' (3.05 m)

Preferred vent hood type

Maximum Length of 4" (10.2 cm) Dia. Flexible Metal Duct

(10.2 cm)

Number

90° turns 2.5"

(6,35

cm)

not recommended

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When sealing the joints of the exhaust ducts with duct tape, the male end of each section

of duct must point away from the dryer to prevent lint buildup. Also, never use screws to

connect the ducts together; this will cause lint buildup. Any ductwork that runs through an

unheated area or is near air conditioning must be insulated to prevent condensation and lint

buildup.

FIGURE 20-12

Make sure that the

male ittings are

installed in the correct

direction.

Correct Incorrect

FIGURE 20-13

Some examples of

correct and incorrect

exhaust duct

installations.

Correct Incorrect

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SAFET Y NOT E All exhaust ductwork must exhaust to the outside of a building to prevent lint

buildup and fire. Do not terminate exhaust ductwork in a chimney, any gas vent, under enclosed

floor (crawl space), common duct with a kitchen exhaust, or into an attic because the lint

accumulation will cause a fire. Finally, never block incoming or exhausted air supplies; this will

cause the dryer to run inefficiently and may cause a fire.

Step-by-Step Troubleshooting by Symptom Diagnosis

In the course of servicing an appliance, don’t overlook the simple things that might be

causing the problem. Step-by-step troubleshooting by symptom diagnosis is based on

diagnosing malfunctions, with possible causes arranged into categories relating to the

operation of the dryer. This section is intended only to serve as a checklist to aid you in

diagnosing a problem. Look at the symptom that best describes the problem that you are

experiencing with the dryer, and then correct the problem.

Dryer Will Not Run

• Do you have the correct voltage at the dryer?

• Test the door switch for continuity of the switch contacts.

• Test for continuity of the motor windings. Also check for a grounded motor.

• Test the timer for continuity of the switch contacts.

• Test the “push to start” switch for continuity of the switch contacts.

• Check for broken or loose wiring. Also check the wire terminal connections that

connect to the different components.

• For electronic control models, check for an error code. Check the electronic control

board.

No Heat

• Do you have the correct voltage? The motor in a dryer runs on 120 volts. The heating

element works on 240 volts; compact models run on 120/240 volts. Check voltage at

the wall receptacle. Also check the nameplate voltage rating for the model that you

are working on.

• Check for any in-line fuses that might have blown. Refer to the wiring diagram,

located on the rear of the dryer or behind the console panel.

• Are the thermostats functioning properly?

• Test the timer for continuity of the switch contacts.

• Test for continuity of the motor windings. Also test for a grounded motor.

• Test the heating element for continuity.

• Test the temperature selector switch for continuity.

• Check for broken or loose wiring.

• Check the exhaust vent duct system.

• For electronic control models, check for an error code.

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Drum Will Not Rotate

• Check the drive belt. Is it broken or worn?

• Check the idler pulley. Is the pulley seized up?

• Check the drum support bearings. Be sure that they rotate freely.

• Is the dryer overloaded with clothing?

• Check for foreign objects that might be lodged between the drum and the

bulkheads.

• For electronic control models, check for an error code.

Dryer Is Noisy

• Check for loose components. Is everything secure and in its proper place?

• Check the idler pulley. Lint buildup can cause the idler pulley shaft to squeak.

• Check the drive belt. Is the belt partially torn?

• Check the drive motor. Is the pulley secured to the shaft? Also check the fan

assembly. Is it loose?

• Check for lint or foreign objects lodged between the drum and the bulkheads.

• Check the front and rear bearings.

• Check the blower assembly. Be sure that the blower wheel is tight on the motor

shaft end.

• Is the dryer level?

Dryer Runs and Heats, but the Clothes Won’t Dry

• Check for a defective thermostat. Use a thermometer to check the duct temperatures

during the cycling of the dryer.

• Check for a loose pulley or blower wheel. Inspect and tighten the blower wheel.

• Check for restricted air flow in the dryer.

• Check the exhaust vent duct system.

• For electronic control models, check for an error code.

Clothes Too Hot or Fabric Damage

• Check the exhaust system for restrictions.

• Check for air leaks in the ductwork and the front and rear seals on the drum.

• Check the thermostats.

• Check the temperature setting with the customer.

• Check the door latch and strike.

• Inspect the interior of the drum for any foreign objects protruding into it.

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Common Drying Problems

The drying of clothes can be affected by several factors:

• Clogged lint screen.

• Exhaust duct too long, collapsed, or crimped.

• Dryer air is exhausted into the area where the dryer is located. For example, the

dryer is located inside a closet and operating with the closet door closed.

• Overloading of clothing in the dryer.

• Dryer is located in an area where the temperature is below 45 degrees Fahrenheit.

• Laundry washed in cold water will take slightly longer to dry.

• The moisture content of certain clothes. Towels and denim retain more moisture,

for example.

• Wrong spin speed selected for the type of laundry being washed. For example, towels,

denim, blankets, small rugs, etc. use the normal wash setting to extract most of the

water from the laundry. If there is an extra option for high-speed spin it should also

be selected to extract as much water as possible from the laundry. The drying cycle

will be increased greatly if the permanent press cycle or the gentle cycle is selected

for these items.

• Electric supply is less than what is needed to operate the dryer efficiently.

• Load type (towels, bedspreads, jeans, etc.)

All of these must be taken into account when diagnosing a complaint of clothes not

drying properly.

Lint

Lint consists of fibers that have broken away from the fabric. It can collect inside the dryer

cabinet and base and create a fire hazard. This lint should be removed every one to two

years by cleaning it out. Some lint can also collect in the door opening, the drum, the heater

assembly, the blower assembly, and the duct assembly. This accumulation of lint should be

removed periodically when performing maintenance on the dryer; otherwise, it could create

problems with the future use of the dryer.

The lint screen should be cleaned every time the dryer is used. The duct system that

exhausts the air to the outside of the dwelling should also be cleaned out every one to

two years.

Shrinkage

Shrinkage is caused by overdrying and by the type of fabric being dried. To reduce the

shrinking of cotton and rayon knits, it is recommended that the user remove them from the

dryer while the clothing is still damp and lay them on a flat surface to air-dry.

Also, you might suggest that the user set the heat setting on a lower setting. Before

drying any synthetic clothing in a dryer, the user should read the label on the garment for

the proper drying instructions and for the proper heat selection. The user should also read

the use and care manual for the proper instructions when operating the dryer.

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Stains

Greasy-looking stains are often caused by:

• Fabric softener that is designed for use in the dryer.

• Fabric softener that was undiluted when the clothes were washed.

• Not enough detergent being used in the wash. This will cause the soil in the water

to stick to the outer tub and to return to the next load being washed.

• Drying of clothing that already has a stain on it.

Brown stains on the clothing are often caused by:

• Fabric softener that is designed for use in the dryer.

• Leaving the wash in the washer tub after the cycle is completed.

• Leaving the wet clothing in the dryer for an extended amount of time.

• A leaking transmission seal.

Static Electricity

Static electricity in the clothes is caused by overdrying them. To reduce this condition, you

must instruct the user to reduce the amount of time the clothes are to be dried and to use a

lower temperature setting. Static electricity in synthetics is normal. To reduce this condition,

use a liquid fabric softener in the wash cycle or use a fabric softener that is designed for use

in the dryer.

Wrinkling

Wrinkling of the clothes is often caused by:

• Not using the permanent press cycle, which has a cooling-down period during

which the heating element is not on.

• Clothing not removed from the dryer after it has completed the cycle.

• Overloading the dryer. The clothes need room to tumble freely without getting

tangled.

• The quality of the permanent press material in the garment might be poor.

• On some models that have steam, check the water supply, water valve, and

steam port.

Electric Dryer Maintenance

Automatic dryers must be cleaned periodically. The excess lint must be removed to prevent

the possibility of a fire and the possibility of the dryer not functioning properly. Most

models have a service panel on the front of the dryer for accessibility. The outside of the

cabinet should be wiped with a damp cloth. It is recommended that the components be

inspected for wear and tear; if repairs are needed, they should be made as soon as possible.

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Repair Procedures

Each repair procedure is a complete inspection and repair process for a single dryer

component, containing the information you need to test a component that might be faulty

and to replace it, if necessary.

Any person who cannot use basic tools should not attempt to install, maintain, or repair

any electric dryer. Any improper installation, preventative maintenance, or repairs will

create a risk of personal injury, as well as property damage. Call the service manager if

installation, preventative maintenance, or the repair procedure is not fully understood.

Dryer Timer

The dryer timer is an electromechanical component controlled by a synchronous motor in

incremental advances. It controls and sequences the numerous steps and functions involved

in each cycle.

The typical complaints associated with the dryer timer are:

• The dryer will not run at all.

• The clothes are not drying.

• The dryer will not stop at the end of the cycle.

• The timer will not advance through the cycle.

To handle these problems, perform the following steps:

1. Verify the complaint. Verify the complaint by operating the dryer through its cycles.

Before you change the timer, check the other components controlled by the timer. If

the dryer will not power up, locate the technical data sheet behind the control panel

or for diagnostics information. On some models you will need the actual service

manual for the model you are working on to properly diagnose the dryer.

2. Check for external factors. You must check for external factors not associated with

the appliance. Is the appliance installed properly? Does the appliance have the

correct voltage? The voltage at the receptacle is between 198 volts and 264 volts

during a load on the circuit (see Chapter 6).

3. Disconnect the electricity. Before working on the dryer, disconnect the electricity.

This can be done by pulling the plug from the electrical outlet. Or disconnect the

electricity at the fuse panel or at the circuit breaker panel. Turn off the electricity.

WARNING Some diagnostic tests will require you to test the components with the power turned on.

When you disassemble the control panel, you can position it in such a way that the wiring will

not make contact with metal. This act will allow you to test the components without electrical

mishaps.

4. Remove the console panel to gain access. To gain access to the timer, remove the

screws that secure the console to the top of the dryer (Figure 20-14). On other

models, to gain access, remove the back panel behind the console.

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5. Test the timer. There are two ways to check the timer:

• Connect a 120-volt fused service cord to the timer motor to see if the timer motor

is operating (Figure 20-15). Connect the ground wire of the 120-volt fused service

cord to the console ground. Be cautious when working with live wires. Avoid

getting shocked. The timer motor operates on 120 volts. If the motor does not

operate, replace the timer. If the timer motor runs but does not advance the

cams, the timer has internal defects and should be replaced.

• Set the ohmmeter range to R × 100, disconnect the timer motor leads, and

check for resistance (Figure 20-16). The meter should read between 2000 and

3000 ohms. Next, test the timer switch contacts with the wiring diagram’s

configuration for the affected cycle. Place the meter probe on each terminal being

tested, and turn the timer knob. If the switch contact is good, your meter will

show continuity.

6. Remove the timer. To remove the timer, pull the timer knob from the timer stem;

then remove the timer mounting screws. Remove the wire lead terminals from the

timer. Mark the wires as to their location on the timer. Some timers have a quick

disconnect, instead of individual wires, which makes it easier to remove the timer

wires (Figure 20-17).

7. Install a new timer. To install a new timer, just reverse the disassembly procedure,

and reassemble. Replace the wires on the timer. Reinstall the console panel, and

restore the electricity to the dryer. Test the dryer for proper operation. Make sure to

take the dryer out of the service test mode when the repair is completed.

(a) (b)

Temperature

selector

Timer

Start switch

FIGURE 20-14 To gain access to the component, remove the screws. Rest the console panel on its face to

gain access to the component.

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Grounded to

console chassis

On/Off

switch

Male plug

with ground

Grounded to

electrical box

20-amp

resettable fuse

120-volt

receptacle

6-foot

service cord

120-volt fused

service cord

Electrical box

24-inch

test leads

Motor terminal

Motor wire

Motor terminal

FIGURE 20-15 The test cord attached to the timer motor leads.

FIGURE 20-16 Checking for continuity between the timer motor and the switch contacts.

Multitester

Timer motor

Timer

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Electronic Control Board and User Interface Controls

On some models the electronic control board and user interface controls replace the

electromechanical timer and rotary selection switches.

The typical complaints associated with the electronic control board or the user interface

controls are:

• The dryer won’t run or power up.

• Unable to program the dryer.

• The display board will not display anything.

• One or more key pads will not accept commands.

• Unusual display readouts.

• Unusual display readouts and/or error codes.

To prevent electrostatic discharge (ESD) from damaging expensive electronic components,

follow the steps in Chapters 6 and 11.

To handle these problems, perform the following steps:

1. Verify the complaint. Verify the complaint by operating the dryer. Turn off the

electricity to the appliance and wait for two minutes before turning it back on. If a

fault code appears, look up the code. If the dryer will not power up, locate the

technical data sheet behind the control panel or for diagnostics information. On

some models you will need the actual service manual for the model you are working

on to properly diagnose the dryer. The service manual will assist you in properly

placing the dryer in the service test mode for testing the dryer functions.

2. Check for external factors. You must check for external factors not associated with

the appliance. Does the appliance have the correct voltage? The voltage at the

receptacle is between 198 volts and 264 volts during a load on the circuit (see

Chapter 6).

Timer plug

Timer

Timer mounting screws

FIGURE 20-17

Remove the timer dial.

Then remove the timer

mounting screws, and

lift the timer off the

mounting bracket.

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3. Disconnect the electricity. Before working on the dryer, disconnect the electricity.

This can be done by pulling the plug out of the wall receptacle. Or disconnect the

electricity at the fuse panel or circuit breaker panel. Turn off the electricity.

WARNING Some diagnostic tests will require you to test the components with the power turned on.

When you disassemble the control panel, you can position the panel in such a way so that the

wiring will not make contact with metal. This will allow you to test the components without

electrical mishaps.

4. Remove the console panel to gain access. Begin by removing the screws from the

dryer top (for front-loading models only) to gain access to the electronic control

board. Remove the console panel screws to gain access to the user interface controls

(Figure 20-18). On top-loading models, the console will roll upwards or toward you

after you remove the console screws.

5. Test the electronic control board and user interface controls. If you are able to run

the dryer diagnostic test mode, check the different functions of the dryer. Use the

technical data sheet for the model you are servicing to locate the test points from the

wiring schematic. Check all wiring connections and wiring. Using the technical data

sheet, test the electronic control or user interface controls, input voltages, and output

voltages. On some models, fuses are soldered to the printed circuit board (PCB).

These fuses must be tested first before condemning the component.

6. Remove the electronic control board and user interface controls. To remove the

defective component, remove the screws that secure the board to the control panel

or dryer frame. Disconnect the connectors from the electronic control board or user

interface control.

7. Install the new component. To install a new electronic control board or user interface

control, read the parts data sheet that comes with the part for the proper installation

process, and just reverse the disassembly procedure and reassemble. Reinstall the

console panel, and restore the electricity to the dryer. Make sure that the dryer in

not in the service mode. Test the dryer operation. Make sure to take the dryer out of

the service test mode when the repair is completed.

Dryer Motor

The dryer motor on most models is a dual-shaft, single-speed, ¼-horsepower, 1725-rpm

motor with an automatic thermal reset protector. One side of the motor shaft is threaded to

hold the blower wheel, and the opposite end of the shaft holds the belt pulley, which is

pressed onto the shaft. Inside the motor is a centrifugal switch, which serves three purposes.

It disengages the motor start winding when the motor reaches 75 percent of its rated speed,

engages the run winding, and closes the circuit for the heater element. On other models,

there are dual motors (Figure 20-2): one is dedicated to the drum and the other is dedicated

to the blower assembly. The purpose of the dedicated motor for the blower assembly is to

be able to alter the blower wheel speed whenever necessary to optimize air flow within

the dryer.

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The typical complaints associated with motor failure are:

• Fuse is blown or the circuit breaker trips.

• Motor will not start; it only hums.

• The dryer will not run.

8 11

1. Electronic control board assembly

3. Knob

4. Program light pipe

5. Auxiliary interface board

6. Pin

8. Push button

9. Push button

11. Push button

12. Push button spring

13. Start light pipe

15. Light pipe

16. Light pipe

19. Screw

22. Interface board wiring harness

23. Wiring harness

29. Control panel

39. Screw

53. Top panel

55. Digital display lens

56. Digital display light pipe

57. Digital display (LED)

FIGURE 20-18

An exploded view of

the electronic controls

in a front-loading

dryer.

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To handle these problems, perform the following steps:

1. Verify the complaint. Verify the complaint by operating the dryer through its

cycles. Listen carefully, and you will hear if there are any unusual noises or if the

circuit breaker trips. On electronic models, turn off the electricity to the appliance

and wait for two minutes before turning it back on. If a fault code appears, look up

the code. If the dryer will not power up, locate the technical data sheet behind

the control panel or for diagnostics information. On some models you will need the

actual service manual for the model you are working on to properly diagnose the

dryer. The service manual will assist you in properly placing the dryer in the service

test mode for testing the dryer functions.

2. Check for external factors. You must check for external factors not associated with

the appliance. Is the appliance installed properly? Does the appliance have the

correct voltage? The voltage at the receptacle is between 198 volts and 264 volts

during a load on the circuit (see Chapter 6).

3. Disconnect the electricity. Before working on the dryer, disconnect the electricity.

This can be done by pulling the plug from the electrical outlet. Or disconnect the

electricity at the fuse panel or at the circuit breaker panel. Turn off the electricity.

4. Gain access to the motor. In order to gain access to the motor, the top must be

raised (Figure 20-19) by removing the screws from the lint screen slot. Insert a putty

knife about two inches from each corner; then disengage the retaining clips and lift

the top. On some models, the top is held down with screws (see inset in Figure 20-19).

Remove the screws and lift the top. Now the front panel of the dryer must be removed

(Figure 20-20). To remove the top panel, insert a putty knife and disengage the

retaining clip (Figure 20-20a).

On some models, the top panel is held in place with two screws. As Figure 20-20b

shows, remove the screws that hold the lower part of the front panel in place. Next,

remove the screws that hold the upper part of the front panel in place (Figure 20-20c),

and then disconnect the door switch wires (label them). With the front panel out of

the way, you can now disconnect the drive belt (Figure 20-21). Push on the idler

pulley to release the tension from the drive belt, and remove the belt from the motor

pulley. Grab the drum and remove it from the cabinet (Figure 20-22). On some models,

you will have to remove the back panel because the drum comes out through the

rear of the cabinet.

5. Disconnect the motor wire leads. Disconnect the motor wire leads from the wiring

harness. Set the ohmmeter on R × 1. Figure 20-23 illustrates testing the motor

windings and the centrifugal switch for continuity. When testing for resistance on the

motor, test from the common wire lead to the run winding. Then test for resistance

from the common wire lead to the start winding. Next, test for resistance from the

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Lint screen slot

Screw holes

(a)

(b) (c)

Door

switch

wires

FIGURE 20-19

Insert a putty knife to

disengage the

retaining clips that

hold the top down.

Don't forget to remove

the two screws under

the lint screen cover.

On some models,

remove the screws

from underneath the

top (see insert).

FIGURE 20-20 Remove the top panel. Remove the screws from the lower front panel. Remove the

screws from the upper front panel. Remember to remove the door switch wires.

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Drum

Idler pulley

Motor pulley

FIGURE 20-21

Push the idler pulley

assembly toward the

drive motor pulley to

release the belt

tension. Then

disconnect the drive

belt from the idler

pulley and drive motor

pulley.

FIGURE 20-22

Remove the drum

from the dryer cavity.

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start winding to the run winding. To test for a grounded winding in the motor, take

the ohmmeter probes and test from each motor wire lead terminal to the motor

housing. The ohmmeter will indicate continuity if the windings are grounded. If the

ohmmeter reading shows no resistance between the motor windings, then replace the

motor. If the motor checks out okay, then check the timer.

6. Remove the motor. To remove this type of motor, you must first disconnect the

blower assembly by holding the motor shaft stationary and then turning the

blower wheel to remove it from the rear of the motor shaft (Figure 20-24). Then

remove the spring clamps that hold the motor in the motor bracket (Figure 20-25).

On some models, the motor pulley must be removed (new motors come without the

pulley attached) by loosening the allen set screw.

FIGURE 20-23

Test the centrifugal

switch and drive motor

windings.

FIGURE 20-24

Disconnect the blower

assembly from the

drive motor shaft.

Multitester

Motor

Centrifugal

switch

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7. Install the new motor. To install the new motor (Figure 20-26), just reverse the

disassembly procedure, and reassemble. Then reassemble the dryer in the reverse

order of its disassembly. Restore the electricity to the dryer and test the motor. Make

sure to take the dryer out of the service test mode when the repair is completed.

Drive Belt

The drive belt extends from the motor pulley, past the idler pulley, and around the perimeter

of the dryer drum. The tension on the belt is maintained by the idler pulley and driven by a

pulley attached to the one end of the motor shaft.

Motor pulley bracket

Spring clamp

Rubber cushion

FIGURE 20-25

Hold the motor and

remove the spring

clamps.

FIGURE 20-26

Place the motor in the

cradle and position it

to it into the slots

properly.

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The typical complaints associated with belt failure are:

• The drum will not turn.

• Dryer motor spins freely.

• It smells like something is burning.

To handle these problems, perform the following steps:

1. Verify the complaint. Verify the complaint by operating the dryer through its

cycles. Listen carefully, and you will hear if there are any unusual noises. Then, with

the door open, press the door switch and start the dryer. The drum should rotate.

On electronic models, turn off the electricity to the appliance and wait for two

minutes before turning it back on. If a fault code appears, look up the code. If the

dryer will not power up, locate the technical data sheet behind the control panel or

for diagnostics information. On some models you will need the actual service

manual for the model you are working on to properly diagnose the dryer. The

service manual will assist you in properly placing the dryer in the service test mode

for testing the dryer functions.

2. Check for external factors. You must check for external factors not associated with

the appliance. Is the appliance installed properly? Does the appliance have the correct

voltage? The voltage at the receptacle is between 198 volts and 264 volts during a

load on the circuit (see Chapter 6). Check for foreign objects lodged between the

drum and bulkhead, etc.

3. Disconnect the electricity. Before working on the dryer, disconnect the electricity.

This can be done by pulling the plug from the electrical outlet. Or disconnect the

electricity at the fuse panel or at the circuit breaker panel. Turn off the electricity.

4. Gain access to the drive belt. To gain access to the drive belt, the top must be raised

(see Figure 20-19) by removing the screws from the lint screen slot. Then insert a

putty knife about two inches from each corner, disengage the retaining clips, and

lift the top. On some models, the top is held down with screws (see the inset in

Figure 20-19). Remove the screws and lift the top. Now the front panel of the dryer

must be removed (see Figure 20-20). To remove the top panel, insert a putty knife

and disengage the retaining clip (see Figure 20-20a). As shown in Figure 20-20b,

remove the screws that hold the lower part of the front panel in place. Next, remove

the screws that hold the upper part of the front panel in place (see Figure 20-20c),

and then disconnect the door switch wires.

5. Remove the drive belt. To remove the drive belt on this type of dryer, you can

disconnect the belt (see Figure 20-21). Push on the idler pulley to release the tension

from the drive belt. Now remove the belt from the motor pulley and from around

the drum (Figure 20-27). If the drive belt is broken, just remove the belt.

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Drive belt

FIGURE 20-27 Removing the drive belt from around the drum.

Dual heaters

Rear of dryer

FIGURE 20-28 Dual-heater element mounted on the rear of the dryer.

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6. Install a new drive belt. To install the new drive belt, just reverse the disassembly

procedure, and reassemble. Then reassemble the dryer in the reverse order of its

disassembly. Restore the electricity to the dryer and test. Make sure to take the

dryer out of the service test mode when the repair is completed.

Heater Element

The heater assembly on some models is located behind the dryer drum (Figure 20-28), while

on other models the heater assembly is located in the back of the dryer, and on other models

the heater assembly is located on the bottom of the dryer (Figure 20-29).

The typical complaints associated with heater failure are:

• The dryer will not dry the clothes properly.

• There is no heat at all when a heat cycle is selected.

• On electronic models, an error code appears.

FIGURE 20-29

Heating element

located on the bottom

of the dryer.

Heating element

enclosed

Thermostat

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To handle these problems, perform the following steps:

1. Verify the complaint. Verify the complaint by operating the dryer through its cycles.

Then open the dryer door, and place your hand inside to see if it is warm in the drum.

On electronic models, turn off the electricity to the appliance and wait for two minutes

before turning it back on. If a fault code appears, look up the code. If the dryer will not

power up, locate the technical data sheet behind the control panel or for diagnostics

information. On some models you will need the actual service manual for the model

you are working on to properly diagnose the dryer. The service manual will assist you

in properly placing the dryer in the service test mode for testing the dryer functions.

2. Check for external factors. You must check for external factors not associated with

the appliance. Is the appliance installed properly? Is the exhaust vent clogged? Does

the appliance have the correct voltage? The voltage at the receptacle is between

198 volts and 264 volts during a load on the circuit (see Chapter 6).

NOT E The dryer motor runs on 120 volts, but the heater works on 240 volts. Check the fuses or the

circuit breakers in the home.

3. Disconnect the electricity. Before working on the dryer, disconnect the electricity.

This can be done by pulling the plug from the electrical outlet. Or disconnect the

electricity at the fuse panel or at the circuit breaker panel. Turn off the electricity.

WARNING Some diagnostic tests will require you to test the components with the power turned on.

When you disassemble the control panel, you can position it in such a way that the wiring will not

make contact with metal. This act will allow you to test the components without electrical mishaps.

4. Gain access to the heater assembly. You must gain access to the heater assembly

through the back. Remove the exhaust duct from the dryer. Then remove the screws

from the back panel (Figure 20-30).

Exhaust

duct

opening

FIGURE 20-30

Remove the screws

that hold the back

panel in place.

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5. Test the heater element. To test the heater element, set the ohmmeter on R × 1.

Remove the wires from the heater (Figure 20-31), and test for continuity. If it checks

out okay, check the thermostats.

6. Remove the heater element. To remove the heater in this type of dryer, you must

first remove the screw and the bracket that holds the heater box in place. It is

located on top of the heater box. You can gain access through the back of the dryer

or lift the top and reach in near the back bulkhead. Then slide the heater box up,

and pull it away at the bottom (Figure 20-32). With the heater box out of the dryer,

remove the screw that holds the heater element in place (Figure 20-33). Pull the

heater element out of the heater box.

7. Install new heater element. To install the new heater element, just reverse the

disassembly procedure, and reassemble. Then reinstall the back panel. Restore the

electricity to the dryer and test it. Make sure to take the dryer out of the service test

mode when the repair is completed.

Door Switch

The door switch is a normally open switch wired in series with the dryer motor. When the

dryer door is closed, the door switch contacts will close completing the circuit through the

run winding of the drive motor.

The typical complaints associated with switch failure are:

• Dryer will not operate at all.

• Dryer light does not work when the door is open.

FIGURE 20-31

Test the heater

element for continuity.

OHMS

6 8 10 15 20 30 50 100

200

5 4 3 2 1 0

OHMS

7 10 15 20

5 4 2 3 1 0

30 50 100 200 500

250

200

150

100

6 4 2 0 2 4 6

Multitester

Heater box

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To handle these problems, perform the following steps:

1. Verify the complaint. Verify the complaint by operating the dryer through its

cycles. Open the door to see if the light is working. On electronic models, turn off

the electricity to the appliance and wait for two minutes before turning it back on.

If a fault code appears, look up the code. If the dryer will not power up, locate the

technical data sheet behind the control panel or for diagnostics information. On

some models you will need the actual service manual for the model you are working

on to properly diagnose the dryer. The service manual will assist you in properly

placing the dryer in the service test mode for testing the dryer functions.

2. Check for external factors. You must check for external factors not associated with

the appliance. Is the appliance installed properly? Does the dryer have the correct

voltage supply? The voltage at the receptacle is between 198 volts and 264 volts

during a load on the circuit (see Chapter 6).

3. Disconnect the electricity. Before working on the dryer, disconnect the electricity.

This can be done by pulling the plug from the electrical outlet. Or disconnect the

electricity at the fuse panel or at the circuit breaker panel. Turn off the electricity.

WARNING Some diagnostic tests will require you to test the components with the power turned on.

When you disassemble the control panel, you can position it in such a way that the wiring will not

make contact with metal. This act will allow you to test the components without electrical mishaps.

4. Gain access to the door switch. You must gain access to the door switch. On this

model, the top must be raised (see Figure 20-19) by removing the screws from the lint

Lower

brackets

Heater

box

Screw

FIGURE 20-32 Remove the heater box. FIGURE 20-33 Remove the heater coil from the

heater box.

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screen slot. Then insert a putty knife about two inches from each corner, disengage

the retaining clips, and lift the top. On some models, the top is held down with screws

(see the inset in Figure 20-19). Remove the screws and lift the top.

5. Test the door switch. The door switch is located in one of the upper corners of the

inside of the front panel (Figure 20-34a). Once you have located the door switch,

disconnect the wires from the terminals. Set the ohmmeter on R × 1, attach the

probes of the ohmmeter to the terminals of the door switch, and then close the door.

With the door closed, there should be continuity. With the door open, the ohmmeter

should not show continuity. Some dryer models have a light inside the drum. This

light circuit is also part of the door switch circuitry. Three terminals are located on

the door switch. Take your ohmmeter probe and place it on the common terminal of

the door switch. To locate the common terminal, read the wiring diagram. It will

indicate which terminal is the common, which is the light, and which is for the

motor circuit. Take your probe and place it on the switch terminal (the light circuit);

then close the dryer door. The reading should indicate no continuity. Now open the

dryer door—you should have a continuity reading on the meter.

6. Remove the door switch. To remove the lever-type door switch (Figure 20-34b);

remove the screws that hold the switch in place. Now lift the switch out from

behind the front panel. To remove the cylindrical type of door switch (Figure 20-34c),

squeeze the retaining clips on the back side of the front panel, and pull out the

switch. To remove the hinge type of door switch (Figure 20-34d), the front panel

must be removed. Next, remove the screws that hold the switch assembly in place.

(a) (b)

Hingemounted

switch

Cylindrical

switch

Lever

switch

Front

panel

FIGURE 20-34

(a) Test the door

switch for continuity.

(b) Remove the

screws that secure

the door switch.

cylindrical door switch.

(d) Removing a hingemounted

door switch.

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7. Install the new door switch. To install the new door switch, reverse the disassembly

procedure, and reassemble. Reassemble the dryer, and install the wires on the new

switch terminals. Plug in the dryer and test it. Make sure to take the dryer out of the

service test mode when the repair is completed.

Thermostat

Thermostats can be mounted on the heater assembly (Figure 20-2 and Figure 20-29) and/or

on the blower assembly (Figures 20-2 and 20-35), or in the inlet filter screen (Figure 20-37).

The thermostats monitor the air temperatures within the dryer drum, exhaust vent, and the

incoming air supply. The thermostats are bimetal switches that are automatic reset, one-time

use, or manual reset.

The typical complaints associated with thermostat failure are:

• The clothes are not drying.

• The dryer will not shut off.

• The dryer will not heat at all.

• The drying temperature is too high.

• Moisture retention (of fabrics) is unsatisfactory.

• On electronic models, an error code appears.

FIGURE 20-35

The thermostat is

mounted on the

exhaust vent pipe

along with the thermal

fuse.

Thermostat

Exhaust vent

Dryer drum

Thermal fuse

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