Test #4C Thermistors - Whirlpool WED99HEDW0 Technical Education

TESTING
WARNING
Electrical Shock Hazard
Disconnect power before servicing.
Replace all parts and panels before operating.
Failure to do so can result in death or
electrical shock.

TEST #4c Thermistors

NOTE: Refer to strip circuit on page 6-16 to diagnose outlet
and compressor thermistors.
Outlet Thermistor
The CCU monitors the exhaust temperature using the outlet
thermistor, and cycles the heater relay on and off, depending
on strategy, to maintain the desired temperature. NOTE: Begin
with an empty dryer and a clean lint screen.
1. Unplug dryer or disconnect power.
2. Remove top panel to access the machine electronics.
3. Remove connector P14 from the CCU and measure the
resistance between P14-3 and P14-6 at the connector. The
following table gives temperatures and their associated
resistance values.
NOTE: All thermistor resistance measurements must be made
while dryer is unplugged and connector removed from CCU.
OUTLET THERMISTOR RESISTANCE
TEMP RES. RANGE
°F (°C) k ohms
50° (10°) 19.0-22.0
60° (16°) 14.8-16.8
70° (21°) 11.5-13.5
¾ If the resistance is OK, the outlet thermistor is good.
Proceed to step 4.
¾ If the thermistor resistance does not agree with the
table, replace the outlet thermistor.
4. Check P14-3 and P14-6 to dryer cabinet ground. If either
pin indicates continuity to ground (short), replace wiring
harness; otherwise, proceed to step 5.
5. If the preceding steps did not correct the problem, replace
the CCU.
Temperature Levels Incorrect – If no error code is displayed
and the connections to the thermistor are good, check the
exhaust temperature value at any or all of the temperature
levels in question, using the Timed Dry cycle.
n
6-14 HybridCare™ Dryer with Heat Pump Technology
For Service Technician Use Only
TEMP RES. RANGE
°F (°C) k ohms
80° (27°) 8.5-10.5
90° (32°) 6.8-8.8
100° (38°) 5.0-7.0
IMPORTANT: Be sure Speed is turned ON before testing.
1. Remove load from dryer.
2. Plug in dryer or reconnect power.
3. Run a TIMED DRY cycle of at least 5 minutes in duration.
Select High, Medium, Low, or Extra Low. Turn on Speed.
4. Using a calibrated temperature probe, take a temperature
measurement in the center of the exhaust outlet. The
correct exhaust temperatures are as follows:
EXHAUST TEMPERATURES
TEMPERATURE HEAT TURNS OFF*
SETTING
High 113° ± 5° (45° ± 3°)
Medium 98° ± 5° (37° ± 3°)
Low 93° ± 5° (34° ± 3°)
Extra Low 86° ± 5° (30° ± 3°)
¾ If the temperature is not reached within ~10 minutes,
check voltage level and for blockage, and then retest.
¾ If the temperature probe does not agree with
temperature setting, replace the outlet thermistor.
¾ If the temperature probe confirms the temperature
setting, retest at a different temperature setting.
5. If the preceding steps did not correct the problem, replace
the CCU.
Compressor Thermistor
1. Unplug dryer or disconnect power.
2. Remove top panel to access the machine electronics.
3. Remove connector P14 from the CCU and measure the
resistance between P14-1 and P14-2 at the connector. The
following table gives temperatures and their associated
resistance values.
NOTE: All thermistor resistance measurements must be
made while dryer is unplugged and connector removed
from CCU.
¾ If the resistance is OK, the compressor thermistor is
good. Proceed to step 4.
¾ If the thermistor resistance does not agree with the
table, replace the compressor thermistor.
COMPRESSOR THERMISTOR RESISTANCE
TEMP °F (°C)
32° (0°)
86° (30°)
104° (40°)
122° (50°)
140° (60°)
158° (70°)
203° (95°)
4. Check P14-1 and P14-2 to dryer cabinet ground. If either
pin indicates continuity to ground (short), replace wiring
harness; otherwise, proceed to step 5.
5. If the preceding steps did not correct the problem, replace
the CCU.
HEAT TURNS ON
°F (°C) °F (°C)
10-15° (6-8°)
below the heat turn
off temperature
RES. RANGE ohms
35975
9786
6653
4608
3243
2332
1093