Maytag 111990" Automatic Dryers Service Manual page 53

connected to the microprocessor board
through edgeboard connector CC (refer
to schematic). Mounted on the blower
cover puts the thermistor in the air flow
of the air being exhausted from the
drum. The increasing or decreasing
temperature of the exhausted air
changes the resistance of the
thermistor. The microprocessor board
uses this input information to control
the heat circuit. On the electric dryer
the microprocessor board controls the
24 DC voltage to the heater relay, on
the gas dryer it controls the L 1 side of
the power supply through edgeboard
connector BB (refer to schematic).
To remove thermistor:
1. Disconnect power supply.
2. Remove front panel.
3" Remove the thermostat cover
mounted to the base (electric dryer
only).
4. Remove the two wires, PK-BK and
PK-BK, from the thermistor.
5. Remove the two screws that attach
the thermistor to the blower cover.
ED/GD401 1090
Check the thermistor:
1. Remove the two wires on the
thermistor, PK-BK and PK-BK.
2. Place ohm meter across these wires
and check resistance of the
thermistor. At room temperature,
77°F, you should read about 10,000
ohms. At 140°F you should read
about 1750 ohms.
Note: Do not check with line voltage
(120 VAC), the thermistor is part of the
low voltage circuitry.
THERMAL FUSES
The function of the thermal fuse and
thermal cut-off is to stop the dryer in
the event an over heating condition
should occur. The electric dryer has a
thermal fuse mounted on the right side
of the heat cone and a thermal cut-off
mounted on the blower cover. The gas
dryer has a thermal cut-off mounted on
the blower cover. Both are referred to
as "thermal fuse" on the electrical
schematic. The thermal fuse and cut-off
are placed in series with the drive
motor. If one of these should open, the
drive motor will stop and the circuit
through the centrifugal switch for the
gas valve / heating element will also
open, breaking the heat circuit. The
thermal fuse and thermal cut-off are not
interchangeable or resettable and must
be replaced after the over heating
problem is corrected.
Note: If one of these thermal devices
opens, it indicates something has
caused an unusual amount of heat to
build up around the device. If this
happens, depending on the model,
REPLACE the hi-limit thermostat and
cycling thermostat or the hi-limit ther-
SECTION 3. SERVICE PROCEDURES
3-25