Exhaust Thermistor; Inlet Thermistor - Whirlpool WED6600VU0 Manual

TECH SHEET - DO NOT DISCARD
TEST #4 Heater
This test is performed when one of the following
situations occur:
Dryer does not heat
Heat will not shut off
Display flashes L2
This test checks the components making up the heating
circuit. The following items are part of this system:
– Harness/connection – Centrifugal switch
– Heater relay

– Exhaust thermistor

– Thermal cut-off – Machine control
electronics. See ESD

– Inlet thermistor/

information, page 1.
high limit thermostat
– User interface
– Heat element
assembly
assembly
Dryer does not heat or display
flashes L2:
Locate the components using figure 2, page 4; and
figure 9, below.
Lint Duct
Drum
Light
Sensor
Harness
Wires Thermal
Connection
Cut-Off (TCO)
4 Duct
Screws
Thermistor Thermal Heat
Fuse Element
Figure 9. Thermal components, viewed
from rear.
1. Unplug dryer or disconnect power.
2. Remove the back panel to access the thermal
components. See Removing the Back Panel,
page 10.
3. Using an ohmmeter and referring to the
appropriate wiring diagram (see pages 11 and
12), measure the resistance across the high limit
thermostat.
If an open circuit is not detected, go to step 5.
If an open circuit is detected, go to step 4.
4. Visually check the wire connections to the ther-
mal cut-off and the high limit thermostat. If con-
nections look good, check for continuity across
each of these components. Replace both the
thermal cut-off and the inlet thermistor/high limit
thermostat assembly if either the thermal cut-off
or the high limit thermostat is electrically open.
FOR SERVICE TECHNICIAN'S USE ONLY
5. Measure the resistance between the red wires at
the heater.
If an open circuit is not detected:
Dual Element Model - Go to step 7.
Single Element or Steam Model - Go to step 9.
If an open circuit is detected, go to step 6.
6. Visually check the wire connections to the heater.
If the connections look good, replace the heater
assembly.
7. Measure the resistance at the heater between the
violet wire and the red wire with the larger
terminal.
If an open circuit is not detected, go to step 9.
If an open circuit is detected, go to step 8.
8. Visually check the wire connections to the heater.
If the connections look good, replace the heater
assembly.
9. Visually check connections at the machine
control electronics. If the connections look good,
and an open circuit was not previously detected
at the heater, remove the P4 connector, then
measure the resistance between P4-3 (red wire)
and P4-6 (red wire) at the connector. See
figure 16, page 9 for connector location; and
Accessing & Removing the Electronic
Assemblies, page 9.
If 5–15 kΩ are measured, replace the
machine control electronics.
If the resistance is less than 1 kΩ, replace the
exhaust thermistor.
Heat will not shut off:
1. Unplug dryer or disconnect power.
2. Access the machine control electronics. See
Accessing & Removing the Electronic
Assemblies, page 9. Remove the P4 connector.
See figure 16, page 9 for connector location;
then measure the resistance between P4-3 (red
wire) and P4-6 (red wire) at the connector.
If 5–15 kΩ are measured, replace the
machine control electronics.
If the resistance is greater than 20 kΩ,
Inlet Thermistor/
replace the exhaust thermistor.
High Limit
Thermostat
TEST #4a Thermistors
EXHAUST THERMISTOR
The machine control electronics monitors the
exhaust temperature using the exhaust thermistor,
and cycles the heater relay on and off to maintain the
desired temperature.
Begin with an empty dryer and a clean lint screen.
1. Plug in dryer or reconnect power.
2. Start the Timed Dry cycle.
3. If after 60 seconds,
display and the dryer shuts off, the thermistor or
wire harness is either open or shorted.
Unplug dryer or disconnect power.
Check wire connections at the machine
control electronics and thermistor. See
Accessing & Removing the Electronic
Assemblies, page 9; and for thermistor
location, figure 9.
4. If
TEMPERATURE
*
5. If the exhaust temperature is not within specified
INLET THERMISTOR
F-22 F-23 The machine control electronics monitors the inlet
or flashes in the
temperature using an inlet thermistor that is part of
the inlet thermistor/high limit thermostat assembly.
1. Activate the diagnostic test mode. See procedure
2. If
If wire connections are OK, check the exhaust
thermistor resistance per step 5.
F-22 F-23
or does not flash in the display, the
connections to the thermistor are good.
Therefore, check the exhaust temperature value
at any or all of the temperature levels in question,
using the Timed Dry cycle, and the following
process:
Hold a glass bulb thermometer capable of
reading from 90° to 180°F (32° to 82°C) in the
center of the exhaust outlet. The correct exhaust
temperatures are as follows:
EXHAUST TEMPERATURES
HEAT TURNS OFF*
SETTING °F (°C)
High
155°±5° (68°±3°)
Medium
140°±5° (60°±3°)
Low
125°±5° (52°±3°)
Extra Low
105°±5° (41°±3°)
The measured overshoot using the glass bulb
thermometer in the exhaust outlet can be 30°F
(17°C) higher.
limits, or you have come here from step 3,
remove the P4 connector, then measure the
resistance between P4-3 (red wire) and P4-6
(red wire) at the connector. See figure 16, page 9
for connector location; and Accessing &
Removing the Electronic Assemblies, page 9.
If the resistance is OK, check P4-3 and P4-6
to machine ground.
If resistance is greater than 0 (zero), replace
wiring harness.
NOTE: All thermistor resistance measurements
must be made while dryer is disconnected from
power.
The following table gives temperatures and
ranges for the associated thermistor resistance
values.
EXHAUST THERMISTOR RESISTANCE
TEMP. RES. TEMP.
°F (°C) kΩ °F (°C)
50° (10°) 19.0–22.0 80° (27°)
60° (16°) 14.8–16.8 90° (32°)
70° (21°) 11.5–13.5 100° (38°)
If the thermistor resistance does not agree
with table, replace the exhaust thermistor.
If the thermistor resistance checks agree with
the measurements in the table, replace the
machine control electronics.
on page 1.
F-24 F-25
or is a displayed error in the
diagnostic test mode, the thermistor or wire
harness is either open or shorted.
Unplug dryer or disconnect power.
PART NO. W10156037A
PAGE 6
HEAT TURNS ON
°F (°C)
10°–15° (6°–8°)
below the
heat turn off
temperature
RES.
kΩ
8.5–10.5
6.8–8.8
5.0–7.0