Maytag MED5800TW - Electric Dryer Technical Education page 73

Thermistor Test Or Dryer Beeps 3 Times
When Push To Start (PTS) Pressed
An electronic temperature sensor called a therm-
istor is used in this model in place of an operat-
ing thermostat. The electronic control monitors
the exhaust temperature using the thermistor,
and cycles the heater relay on and off to main-
tain the desired temperature.
Procedure
Begin with a fully assembled, empty dryer and
a clean lint screen.
1. Set the following configuration:
• Door - must be closed
• Timer dial - Timed Drying
• Temperature switch - High
• Wrinkle Prevent switch - Off
• End of Cycle Signal switch - Louder
2. Press the Push to Start switch.
• If you hear three short beeps and the
dryer shuts off after several seconds,
the thermistor or wire harness is either
shorted or open.
• Unplug dryer or disconnect power.
• Check wire connections at the elec-
tronic control and thermistor.
• If wiring is functional, replace the therm-
istor. Refer to Thermal Components il-
lustrations, page 6-6.
• If the dryer appears to operate correct-
ly, proceed to step 3.
3. Remove exhaust vent and start the dryer.
• Turn Temperature switch to desired
temperature to be tested, and select 20
minutes of Timed Drying. Hold a glass
bulb thermometer capable of reading
from 90°F to 180°F (32°C to 82°C) in
the center of the exhaust outlet. Mea-
sure exhaust temperatures with heater
off and on.
The correct exhaust temperatures are
as follows:
EXHAUST TEMPERATURES
TEMPERATURE
SWITCH
SETTING
High
Normal
Medium, Casual
Medium,
Energy Saver
Low
Ex-Low
*
The measured overshoot using the glass
bulb thermometer in the exhaust outlet
can be 30°F (17°C) higher.
• If the exhaust temperature is not within
specified limits:
- Unplug dryer or disconnect power.
- Disconnect wires from thermistor,
then check the resistance of the
thermistor. The following table gives
temperatures and ranges for their
associated resistance values:
THERMISTOR RESISTANCE
TEMP.
°F (°C)
50° (10°) 19.0–22.0
60° (16°) 14.8–16.8
70° (21°) 11.5–13.5
• If the thermistor resistance does not
agree with table, replace the thermistor.
• If the thermistor resistance checks agree
with the measurements in the table, re-
place the electronic control assembly.
6-7
HEAT TURNS HEAT TURNS
OFF* ON
°F (°C) °F (°C)
155° ± 10°
(68° ± 6°)
145° ± 10°
(63° ± 6°) 10°–15° (6°–8°)
135° ± 10° below the
heat turn off
(57° ± 6°)
temperature
125° ± 10°
(52° ± 6°)
115° ± 10°
(46° ± 6°)
RES. TEMP. RES.
kΩ °F (°C) kΩ
80° (27°) 8.5–10.5
90° (32°) 6.8–8.8
100° (38°) 5.0–7.0