Maytag 111990" Automatic Dryers User manual

Maytag
111990" Automatic Dryers
Service Manual
16000132
Issued 1990
Revised 2/98

Contents
SECTION 1. ELECTRICAL TEST EQUIPMENT " 1-1
APPLIANCE TEST METER 1-1
CLAMP-ON AMMETER '. ....................... .. 1-3
MOTOR TEST CORD 1-4
VOLTAGE CHECKS 1-5
TEMPERATURE READINGS RANGE (50°F.
to 300°F.) 1-6
SECTION 2. ELECTRICAL -MECHANICAL TROUBLESHOOTING
2-1
WILL NOT RUN 2-1
WILL NOT DRY '2-2
WILL NOT SHUT OFF
,............................... 2-2
MISCELLANEOUS
,................................... 2-6
MICROPROCESSOR
BOARD CONTROL MODELS 2-7
DRYER (MICROPROCESSOR BOARD CONTROL)
2-11
FAULT CODE 2-15
SECTION 3. SERVICE PROCEDURES
3-1
ACCESS TO CONTROL PANEL COMPONENTS 3-1
CONTROL PANEL ASSEMBLY COMPONENTS 3-1
MICROPROCESSOR BOARD CONTROL 3-10
FRONT PANEL AND COMPONENTS 3-13
TUMBLER AND RELATED COMPONENTS 3-17
THERMOSTATS 3-24
BLOWER
3··27
DRIVE MOTOR AND IDLER ASSEMBLY ,........................ 3-28
HEATING ELEMENT
AND RELATED COMPONENTS -- ELECTRIC MODELS 3-31
GAS VALVE AND RELATED COMPONENTS 3-34
CABINET AND TOP COVER
3-41
SECTION 4. PRE-INSTALLATION CONSIDERATIONS 4-1
LOCATING DRYER 4-1
EXHAUSTING 4-2
ADJUSTING
MAIN BURNER 4-6
ELECTRICAL REQUIREMENTS 4-8
ELECTRICAL CONNECTIONS 4-10
A!?DITIONAL INFORMATION 4-12
PERSONAL SAFETY PRECAUTIONS
'.' . . .. 4-12
SECTION 5. GENERAL INFORMATION
5-1
HEAT SOURCE 5-1
MODEL CHART 5-2
SCHEMATICS 5-3
ED/GD401 1090 Contents

ED/GD401 1090 Contents
ii

INTRODUCTION
This service manual is intended to assist you in diagnosing conditions which may
develop. Electrical
component testing is for the most part, made with an appliance
test
meter and consists of checking for open or closed circuits. Mechanical checks
are made through sight and sound, along with the use of aclamp-on ammeter.
This manual is designed for the technician who is familiar with the operation and
construction of May tag products. Information contained in this manual is intended
for use by a qualified service technician, familiar with proper and safe procedures
to be followed when repairing an electrical appliance. All tests and repairs should
be performed by a qualified service technician equipped with proper tools and
measuring devices. All component replacements should be made by a qualified
service technician, using only MA yeOR replacement parts.
Improper assembly or adjustment may occur if service or repair is attempted by
persons other than qualified service technicians or if parts other than MA yeOR
replacement parts are used. Improper assembly or adjustment can cause haz-
ardous conditions.
There can be risk of injury or electrical shock while performing services or repairs.
Injury or electrical shock can be serious or even fatal.
The first and most important step of any service call is to accurately determine what
the
complaint is. This is best accomplished by questioning the customer, finding
out what the prodUct is or isn't doing and why they feel a problem exists.
Section 1covers Electrical Test Equipment. This sections also
covers general use
of
the equipment; an Appliance Test Meter, Clamp-On Ammeter and Motor Test
Cord.
Section 2
covers Electrical-Mechanical Troubleshooting and a list of possible com-
plaints. Find
the complaint which you feel best matches that provided by the cus-
tomer and turn to the appropriate page(s). You will find a list of possible electrical
and mechanical
problems for the complaint, which have been listed in there order
\
of:
1. Ease in checking.
2. Probability.
ED/GD401 1090 INTRODUCTION Iii

Systematically eliminating these possibilities will allow you to find and correct the
problem.
Section 3 covers Service Procedures. This section will provide information on
location of components, disassembly and/or reassembly procedures, the purpos,e
and/or function of the part and in some instances specific checks to be made.
Section 4 covers Pre-Installation Considerations. This provides information on
location and exhausting of dryer, main burner adjustment, electrical requirements
and connections.
Section 5 covers General Information. This section covers brief specifications,
cycle descriptions and schematics.
\ ....
ED/GD401 1090 INTRODUCTION iv

SECTION 1. ELECTRICAL TEST EQUIPMENT
The equipment required to service
May tag products depends largely upon
the condition encountered. Locating a
malfunction will often require the use of
electrical testing equipment such as:
•
Appliance Test Meter
• Clamp-on Ammeter
• Motor Test Cord
APPLIANCE TEST METER
Probably the easiest means of testing
electrical components is ~'continuity
testing" with an Appliance Test Meter.
Continuity is a complete or continuous
path from one point in an electrical
circuit to another point.
The
obvious advantages of being able
to check electrical components and cir-
cuits without power applied is one of
the features of the ohmmeter. Multiple
ranges allow accurate determination of
resistances of both single components
and entire circuit paths. Resistance is
measured in "ohms".
An Appliance Test Meter is a multi-
purpose tester combining an AC-DC
voltage tester with a multi-range
ohmmeter.
\
SF
2
APPLIANCE TEST METER
SET METER FOR USE AS FOLLOWS:
1. Calibrate meter by touching test
probes together and turning
adjusting dial until meter reads "0"
on the ohm scale. Recheck cali-
bration whenever adjusting dial for
ohms settings is changed. (Replace
battery
if adjustment will not bring
meter reading to "0".)
2. Select the scale most easily read
and place test
probes on respective
terminals. When checking aswitch,
the reading would normally be
either open or closed. A reading of
70 on the R x 10 scale would for
example be 700 ohms resistance.
ED/GD401 1090 SECTION
1. ELECTRICAL TEST EQUIPMENT 1-1

~f~
~.,~"] Q
CAUTION ---------------,
Always be sure the power has been
disconnected before making resist-
ance
measurements. Failure to do
so will result in damage to your
meter! Internal batteries provide all
the power needed to make resist-
ance checks. They
should be
checked at least once a
year and
replaced as needed.
For the most part, we will only be con-
cerned with continuity. Is there apath
or not? References are made between
a
"closed" (continuity) reading and an
"open" (no continuity) reading. One
note,
when you get an "open" reading,
try a higher resistance range (setting).
A
very high resistance appea~s as an
"open" on the lower ranges. For best
accuracy alw~ys "re-zero" meter when
changing ranges and/or the physical
position of the meter.
Continuity testing, as related to an elec-
\
tricarcomponent, is the check of a part
for an "open" or "closed" circuit.
Electrical components fall into two
general categories.
1. Loads- Devices that use or
consume electricity: Examples
ED/GD401 1090
would include drive motor, heating
elements, lamps,
timer and solenoid
coils.
2.
Switches -Devices that control the
supply of electricity to the load or
loads in a circuit. Examples include
door switches, timer contacts,
selector switch and relay contacts.
Continuity test of "load" devices will
show varying levels of resistance from
very low for some transformer and
motor windings to very high for some
timer motors and components on elec-
tronic control boards. Usually it is
more important to know if there is a
path
for current .flow through a device
(continuity) than to know the exact
resistance (ohms)
of the device.
Continuity tests of switches will show
virtually no resistance, even low values
indicates burned or dirty contacts in a
switch.
Continuity testing is a process of elimi-
nating those electrical components
involved in a given function of the
appliance, until the inoperative part is
found. By reviewing the list of possible
electrical problems under a given con-
dition, and then performing appropriate
continuity checks on the parts involved,
you should be able to locate the elec-
trical component which is inoperative.
When checking components or circuit
paths for continuity, external wiring
should be disconnected to eliminate
false readings through external paths.
Isolate what
you want to test.
The
following shows typical resistance
values for some of the components
found on May tag dryers.
Heating Element -- 10.23 ohms.
SECTION 1. ELECTRICAL TEST EQUIPMENT 1-2

Gas Valve
Disconnect radiant sensor and igniter
wires. Measure across igniter wires or
igniter plug from valve to get a resist-
ance value of -- 425-450 ohms.
Measure across sensor wires to get a
resistance
of -- 450-475 ohms.
Drive Motor
Red terminal to Gray terminal -- 1.5
ohms.
In order to measure the individual
windings the red and gray wires will
have to be pulled off of the start switch.
Run
winding only -- 2.25 ohms.
Start Winding only -- 3 ohms.
Glow Bar Igniter
Because of the make-up of the igniter,
the resistance will vary over a rather
wide range. Values from 180 ohms to
400
ohms would be typical with an
igniter at room temperature.
These values are provided so that you
may have an idea of the resistance that
you can see in testing. These resist-
ances
are not meant to be used as the
exact
values to determine whether a
t;omponent should be replaced. They
\
are provided so that you may have an
idea of the resistance that you can see
in
testing components.
EDIGD401 1090
CLAMP-ON AMMETER
Each circuit in an appliance has a
"normal" current draw which is an indi-
cation of the performance of that circuit.
Current draw levels, less than or more
than normal, give clues to malfunctions.
The clamp-on
ammeter measures these
currents without breaking the circuit by
measuring the strength of the magnetic
field developed around each conductor.
Current is read by separating the con-
ductors and clamping the jaws of the
ammeter around each conductor on
which current is to be read. Low
amperage readings indicate problems
such as damaged heating elements,
etc.
High amperage readings indicate
the unit being tested is operating under
an increased mechanical or electrical
load.
SECTION 1. ELECTRICAL TEST EQUIPMENT 1·3

Note: Overloads on a circuit breaker
or fuse can be traced to the product
being tested or the circuit breaker (or
fuse) by checking the product's current
draw. If the amperage reading is less
than the breaker reading, the breaker
or fuse box is at fault.
USE OF AMMETER ON DRYER
There are two currents of concern to us
in an
electric dryer; the heating
element current and the drive motor
current. These currents can be meas-
ured by use of a "split line cord" exten-
sion for the dryer cord or by attaching
the ammeter to the respective power
line wires at the dryer terminal block.
Current measured should be 21 amps
on the heating element side of the line,
24
amps on the drive motor side of the
line and 4 amps on the center or
neutral line.
A
\".
MOTOR TEST CORD
The motor test cord may be used. to
electrically check operation of the drive
motor while still installed in the unit.
Testing
of the motor in this manner
determines whether or not it will run
independently of other electrical com-
ponents.
Two test leads are required to check
operation of the drive motor. To check
the motor for running, hook up test
cord as shown.
WHORGY
OVERLOAD'- ,
PROTECTOR ( "
,\
START RUN'
\
I \
,START :AD
YEL 0RUN
0--- I
START Q . CENT. SWITCH
~~N 0----- -q-oBLK
BU .... ,', ... /
.......... __ ....
DRIVE MOTOR
Location of terminals on motor may vary from drawing.
ED/GD401 1090 SECTION 1. ELECTRICAL TEST EQUIPMENT 1-4

CHECKING HEAT CONTACTS,
MOTOR CENTRIFUGAL SWITCH
1. Disconnect dryer power source.
2. Gain access to motor and remove
blue and black leads from motor
switch.
3. Use
either of the following test
methods using appropriate caution.
A. Live test -- USE CAUTION
1. Using a double insulated spade con-
nector, connect blue and black wires
removed from motor switch.
2. Reconnect
dryer to power and set
for heat cycle.
3. Start
dryer, if heat is produced,
replace motor switch on motor. If
no heat,
continue additional circuit
checks.
B.
Continuity Check
(Insulate wires removed from motor
sWitch.)
1. Using clip adapters, attach meter
probes to the blue and black motor
switch terminals.
2. Arrange probe leads away from any
moving parts and set meter on RX1
range.
3. Reconnect dryer to power source
and start dryer, continuity on meter
indicates good switch. No conti-
nuity, replace motor switch or
motor.
4. Open door to stop dryer. When
\
motor stops, motor switch contacts
must open, if not replace switch or
motor.
ED/GD401 1090
VOLTAGE CHECKS
For the most part these checks will
consist of taking readings at the wall
receptacle in order to delermine the
availability of voltage to the product.
Voltage checks on individual compo-
nents of a product are not recom-
mended due to the possibility of
electrical shock. Component part
testing is best accomplished through
continuity checks with an Appliance
Test Meter.
Note: Use of the meter on voltage
higher than the indicated range may
cause permanent damage to the meter.
To
prevent damage, first select highest
range for readings which fall within the
lower scale.
SET UP METER FOR USE AS FOLLOWS:
1. Turn selector knob to desired meter
function and appropriate range.
2. Plug black lead into socket marked -
(negative).
3. Plug red
lead into socket marked +
(positive).
4. Place test leads into receptacle in
order to determine voltage avail-
able.
SECTION 1. ELECTRICAL TEST EQUIPMENT 1-5

TEMPERATURE READINGS
RANGE (50°F. to 300°F.)
Air temperature readings can be taken
at
the lint filter by removing the filter
and placing the accessory temperature
probe (Part NO. 38562) directly in the
lint filter opening. Cycling of the ther-
mostats can actually be observed as
can the
temperature of the exhausted
air.
SET UP METER FOR USE AS FOLLOWS:
1. Turn selector knob to TEMP.
2. Insert black negative lead of temper-
ature probe into socket marked -
(negative).
3. Insert red positive lead of temper-
ature probe into socket marked +
(positive).
4. To calibrate meter, touch black plug
from red positive lead to black nega-
tive lead and turn calibration dial
until needle aligns with CAL.
5. Probe is ready to use -- read blue
scale on meter face marked TEMP.
ED/GD401 1090 SECTION
1. ELECTRICAL TEST EQUIPMENT 1-6

SECTION 2. ELECTRICAL -MECHANICAL
TROUBLESHOOTING
WILL NOT RUN
Dryer won't start or run.
• All wires are hooked up to their corre-
sponding terminals.
• Dryer is plugged in.
• Blown fuse or circuit breaker.
• Door switch.
• Push-to-start switch.
• Timer.
• Drive motor.
• Thermal fuse.
Drive motor runs -- drum won't turn.
• Belt off or broken.
• Motor pulley loose or off.
•
Idler tension spring.
• Idler pulley.
Dryer runs a few minutes and then
stops --Motor overload protector
opens.
• Lint build-up around drive motor.
• Low voltage.
• Blower impeller blocked.
e, Drive motor.
\\.
Dryer blows fuses or trips circuit
breaker.
Electric Models
•The amperage readings are at 240
volts. One line will be 24 amps and
the other line will be 21 amps. The
neutral line will be at 4 amps. If you
have the above amperage readings,
the problem is not the dryer. Check
the fuse box, circuit breaker or house
wiring.
• Shorted heating element.
• Incorrect wiring or a wire shorting to
ground.
• Drive motor.
Gas Models
• During ignition the dryer will draw 7
amps. With the burner on, the dryer
will draw 4.5 amps. If the dryer is
drawing the above amperage and the
fuse blows, the problem is not the
dryer. Check the fuse box, circuit
breaker or house wiring.
• Igniter.
• Incorrect wiring or a wire shorting to
ground.
• Drive motor.
CAUTION ---------------------------,
Always disconnect power supply before making any continuity checks or resist-
ance readings.
ED/GD401 1090 SECTION
2. ELECTRICAL -MECHANICAL TROUBLESHOOTING 2.,.1

WILL NOT DRY
Dryer won't heat (motor runs).
ELECTRIC MODELS
•
Blown fuse or tripped circuit breaker.
•Open heating element.
•
Hi-limit thermostat.
• Regulating thermostat.
• Temperature selector switch.
•Timer.
•Cycle
selector switch (where used).
•
Drive motor start switch.
Improper Drying -- Clothes Wrinkled --
Harsh -- Taking too long
• Lint filter is clean.
•Restriction in exhaust.
•Exhaust
hood door stuck.
•Exhaust
too long.
•
Poor make-up air.
• Incorrect drum speed. Adjust motor
pulley or wrong motor pulley.
• Blower impeller bound.
• Be sure element or gas valve cycles
on and off.
•
Shorted heating element - electric
dryers only.
• Customer ove'tloading dryer.
•Check clothing labels for fabric
content.
WILL NOT SHUT OFF
Time Dry Models
• Timer motor.
•Timer.
AUTO DRY MODELS
•Set timer for time dry. Check voltage
across timer motor. If timer will not
advance, replace timer.
•When valve or element cycles off,
should have power to timer motor, if
not, proceed with next check.
•
Dryer cycling on hi-limit thermostat.
Check following.
• Lint filter clean.
•
Restriction in exhaust.
•Exhaust
hood door stuck.
•Exhaust
too long.
•
Regulating thermostat.
• Customer is overloading dryer.
ELECTRONIC CONTROL MODELS
The electronic control and timer are
used to complete the drying cycle and
cool-down period for these dryer
models. The dryer starts out with the
drive motor running, the timer motor
running, the heat cycling and the elec-
tronic control disabled. As the timer
advances to a certain point in the cycle,
CAUTION
-------------------------,
Always disconnect power supply before making any continuity checks or resist-
ance
readings.
ED/GD401 1090 SECTION
2. ELECTRICAL -MECHANICAL TROUBLESHOOTING 2-2

the electronic control becomes opera-
tional as cam number two opens. A
short time later, the timer motor is de-
energized when cam number one for
the timer motor opens. It is during this
stall period that the electronic control
system uses the wet clothes falling
across the sensor in the drum to dis-
charge the capacitor and keep the
dryer running.
There are three dryness levels; More
Dry, Normal Dry and Less Dry. These
dryness levels have been accomplished
by placing resistors on the electronic
control (printed circuit board) and
routing the bypass wiring accordingly.
The level of resistance in the circuit
,
determined by the dryness level
selected, affects
the charge-up rate of
the capacitor and accomplishes the
desired dryness level. As the clothes
get dry, the capacitor is able to build
up a charge to a point where the neon
bulb fires, thus triggering the gate on a
SCR. When
this happens, a circuit is
made through the SCR, energizing the
coil in the relay. This takes only a split
second and the relay's coil is then held
energized through aset of contacts in
the relay.
Also, when the coil in the relay is ener-
gized, the timer motor is activated
through another set of contacts in the
relay. The timer advances and opens
cam number three for the heater and
the dryer begins a timer controlled
CAUTION
cool-down period. The amount of cool-
down time will depend upon the cycle
selected: Regular - 6 minutes,
Permanent-Press -13 minutes and
Permanent-Press with Press Care -33
minutes. NOTE: These times are
approximate. The timer then advances
to where cam number 1A opens, de-
energizing the drive motor and the
cycle ends.
TROUBLESHOOTING
When the dryer does not go into cool-
down and shut off with dry clothes, you
need to know whether you have a
control problem or a sensor problem.
Troubleshooting the electronic control
is made easier if we break the circuit
down into parts. We can separate the
two parts by disconnecting the W-BU
wire in the control panel at the plastic
coupler. The upper part contains the
electronic control assembly which con-
sists of the edgeboard connector
assembly, printed circuit board
assembly and relay. The lower part
consists of the sensor assembly located
on
the tumbler front bulkhead.
Separating the two areas by pulling the
wires apart at the coupler will show
where the problem is located. If the
dryer is started without any clothes in
the drum and shuts off in about 20
minutes without the sensor circuit
hooked up, then the sensor must be
keeping the dryer from shutting off.
Always disconnect power supply before making any continuity checks or resist-
ance readings.
ED/GD401 1090 SECTION 2. ELECTRICAL -MECHANICAL TROUBLESHOOTING 2-3

NOTE: This amount of time is for
Regular Fabrics on a Less Dry setting.
A setting of Normal Dry or More Dry
will add more time before the dryer
shuts off. If the dryer does not shut off,
then the problem is in the electronic
control assembly.
Sensor Assembly
1. Disconnect power supply.
2. Remove front panel.
3. Remove wires going to the sensor
bars.
4. Check with ohmmeter to make sure
there is NO continuity across the
sensor bars. If you have continuity
across the sensor bars the capacitor
cannot build a charge, it will contin-
ually bleed off.
CAUTION
Always disconnect power supply
before making continuity or
resistance checks.
5. Check to make sure the sensor bar
(the one not connected to cabinet
ground) is not shorted to cabinet
ground. If this sensor bar has a
leakage path to cabinet ground, the
capacitor cannot build a cllarge and
will continually bleed off. Use
ohmmeter to ~heck from sensor bar
to cabinet ground.
Electronic Control Assembly
If dryer does not go into cool-down and
shut off with the sensor disconnected
the problem is in the electronic control
assembly. While the dryer is running,
observe the neon bulb on the electronic
control (printed circuit board). When
the capacitor reaches approximately 72
volts, the neon bulb "fires" (flashes),
the SCR conducts, the relay coil is
energized and the contacts in the relay
close.
If neon bulb "FIRES" but timer does
not advance (timer motor is not ener-
gized):
1. Check relay coil for continuity or
resistance.
A. Disconnect power supply.
B. Remove BK and BR wires from
relay (refer to electrical wiring
diagram).
C. Attach meter leads across these
terminals and complete check. If
checking resistance, you should see
about 2200 ohms of resistance. No
continuity, replace relay.
2. Check continuity across contacts
O-BK to RD in relay. When closed,
this set of contacts is used to keep
the coil energized.
A. Disconnect power supply.
B. Remove wires O-BK and RD
from relay.
CAUTION --------------------------,
Always disconnect po~er supply before making any continuity checks or
resistance readings.
ED/GD401 1090 SECTION
2. ELECTRICAL -MECHANICAL TROUBLESHOOTING 2-4

C. Remove BK wire from buzzer.
D. Attach motor test cord to the BK
wire (removed from buzzer) and to
the O-BK wire (removed from relay).
E. Plug motor test cord into outlet
(coil in relay should now be ener-
gized).
F. Check for continuity from ter-
minal RD on relay to terminal O-BK
on relay. No continuity, replace
relay.
CAUTION SHOULD BE EXERCISED
WHENEVER WORKING AROUND
LIVE VOLTAGE.
3. Check continuity across contacts
W-BK to RD in relay. When closed,
this set of contacts is used to ener-
gize the timer motor by bringing the
neutral side of the power supply
through the relay, to the timer
motor.
A. Disconnect power supply.
B. Remove wires W-BK, O-BK and
RD from relay.
C.
Remove BK wire from buzzer.
D. Attach motor test cord to the BK
wire (removed from buzzer) and to
the O-BK wire (removed from relay).
E. Plug motor test cord into outlet
(coil in relay should now be ener-
gized).
\"-
CAUTION
F. Check for continuity from ter-
minal RD on relay to terminal W-BK
on relay. No
continuity, replace
relay.
4. Replace electronic control (printed
circuit board).
If neon bulb does not "FIRE":
1. Check capacitor.
A. Disconnect power supply.
B. Remove electronic control
(printed circuit board).
C. Set ohmmeter to an ohm scale,
such as Rx100.
D. Place meter leads into openings
in the edgeboard connector where
capacitor leads terminate. First,
make sure you have discharged the
capacitor by shorting the leads. Use
a
piece of insulated wire with the
ends stripped.
E. Needle should deflect to one side
and then slowly drop back to zero.
F. Failure to deflect the needle
would indicate an open capacitor.
Failure of the needle to drop back
would indicate a shorted capacitor.
Replace edgeboard connector
assembly.
2. Replace electronic control (printed
circuit board).
Always disconnect power supply before making any continuity checks or resist-
ance readings.
ED/GD401 1090 SECTION 2. ELECTRICAL -MECHANICAL TROUBLESHOOTING 2-5

MISCELLANEOUS
Dryer noisy.
• Thumping sound. Check for loose
drum baffle.
•
Thumping sound. Rear drum roller(s)
worn or misaligned.
• Thumping sound. Check drum for
rough spots.
•Ticking
sound. Loose wire hitting
cabinet or other component.
•Ticking sound. Check for an object
caught in the blower.
• Scraping sound. Front or rear
bulkhead felt seal out of position.
• Scraping sound. Teflon bearings
mounted to the front bulkhead worn.
•Popping or squealing sound. Check
for asticky belt or frayed belt.
Buzzer will not buzz at end of cycle.
(Auto Dry Models)
• Be sure all wires are connected and
wired correctly on the timer, buzzer
and drive motor.
•Buzzer.
•
Motor centrifugal switch sticking in
run position.
Buzzer stays on too long or goes off
too quickly.
(Auto Dry Models)
• Length of time the buzzer stays on is
dependent upon the time it takes the
motor to slow down, allowing the
motor switch to reset. The normal
time increment is between 2 and 3
seconds.
Buzzer will not buzz during Press Care
Setting.
•With dial set on auto dry permanent
press and the press care "on" button
depressed, the buzzer will sound at
the end of the normal 14 minute cool-
down. After this, the dryer will con-
tinue to tumble clothes in cool air for
24 minutes. If buzzer does not sound,
proceed on.
•
Buzzer signal on.
•
Miswired press care switch or timer.
•Buzzer.
•
Timer.
Buzzer will not periodically buzz during
permanent press cool down.
•Timer.
CAUTION
---------------~---------,
Always disconnect power supply before making any continuity checks or resist-
ance readings.
ED/GD401 1090 SECTION 2. ELECTRICAL -
MECHANICAL TROUBLESHOOTING 2-6

MICROPROCESSOR BOARD
CONTROL MODELS
The microprocessor board receives
input information from the various com-
ponents involved with the operation of
the dryer; such as the dryness sensor
and the thermistor. It uses this infor-
mation to determine the necessary
control for the completion of the cycle.
One
of the ways it accomplishes this is
through the use of control relays. A
control relay (S.P.S.T.) is placed in the
motor circuit for both the gas and elec-
tric dryer. Another relay (S.P.S.T.) is
placed
in the heat circuit for the electric
dryer only. With these relays the
microprocessor board is capable of
using a low voltage circuit to control a
high voltage circuit. We can call these
two circuits the control circuit and the
controlled circuit. NOTE: The control
for the gas dryer's gas valve circuit is
different and is covered later.
The
control circuit for the drive motor
consists of the microprocessor board
and the Motor Relay's coil. The con-
trolled circuit for the drive motor con-
sists
of the Motor Relay's switch
contacts, thermal fuse and cut-off drive
,
motor and door switch. The micro-
processor board starts the drive motor
by sending 24 VDC to the Motor
Relay's coil. When energized, the coil
creates a magnetic field that closes the
CAUTION
switch contacts in the relay and pro-
vides apath for voltage to the motor.
When the microprocessor board deter-
mines it needs to stop the motor, it
removes the 24 VDC to the relay's coil.
The
switch returns to its normally open
position and the path for voltage to the
motor is opened.
The control circuit and controlled circuit
for the heating element on the electric
dryer operate on the same principle as
the motor relay's circuits. When the
microprocessor board wants to ener-
gize the heating element it sends 24
VDC to
the coil in the Heater Relay and
apath for voltage is completed through
the switch contacts to the heating
element. When the 24 VDC are
removed from the coil the switch con-
tacts
open and the path for voltage to
the heating element is opened.
TROUBLESHOOTING
When trying to determine what is
causing the problem (drive motor will
not run or heating element will not
come on), separate the two circuits to
isolate the problem area. Start with the
control circuit (it has to function before
the controlled circuit will work). Deter-
mine what is involved in this circuit and
proceed to check the components. If
these components are found to be func-
tioning correctly, focus on the con-
trolled circuit. Determine what is
involved and proceed in checking the
components.
Always disconnect power supply before making any continuity checks or resist-
ance readings.
ED/GD401 1090 SECTION
2. ELECTRICAL - MECHANICAL TROUBLESHOOTING 2-7

CONTROL CIRCUIT
Drive motor will not run (gas and elec-
tric):
1. Disconnect the power supply.
CAUTION
Always disconnect power supply
before making continuity or
resistance checks.
2. Make continuity check or resistance
check on
Motor Relay's coil.
A. Remove
wire connectors O-BK
and W-BU on
the Motor Relay.
B. Attach
meter leads across termi-
nals O-BK and W-BU. You should
see about 470 ohms of resistance if
checking resistance.
C. No continuity, replace the relay.
CAUTION:
Use extreme care when checking
voltage.
3. Check for 24 VDC across the coil on
the Motor Relay. To check for this
voltage the dryer has to be in a
program.
A. Place meter leads across wire
connectors O-BK and W-8U on the
Motor Relay (the relay has two sizes
of terminals; the smaller terminals
for DC and the larger terminals for
AC).
\. CAUTION
Note: You are checking DC voltage,
set and use
meter accordingly.
B. No voltage, suspect the micro-
processor, transformer, edgeboard
connector AA or power supply.
CONTROLLED CIRCUIT
1. Check for continuity across the
Motor Relay's switch contacts with
the coil energized.
A. Disconnect power supply.
B. Remove wire connectors R-BK
and GY.
C. Attach the meter's leads across
terminals R-BK and GY.
D. Connect
power supply_
CAUTION SHOULD BE EXERCISED
WHENEVER WORKING AROUND
LIVE VOLTAGE.
E. No continuity across switch con-
tacts with coil energized, replace the
relay.
2. Another method of checking.
A. Disconnect the power supply.
B. Remove and connect wires R-BK
and GY together (the wires connec-
tors are insulated, a jumper will
have to be used).
_ ...... ,~
Always disconnect power supply before making any continuity checks or
resistance readings.
ED/GD401 1090 SECTION
2. ELECTRICAL -MECHANICAL TROUBLESHOOTING 2-8