Maytag MED5800TW Technical Education - Page 73

Thermistor Test Or Dryer Beeps 3 Times, When Push To Start PTS Pressed, Procedure

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Thermistor Test Or Dryer Beeps 3 Times When Push To Start (PTS) Pressed An electronic temperature sensor called a thermistor is used in this model in place of an operating thermostat. The electronic control monitors the exhaust temperature using the thermistor, and cycles the heater relay on and off to maintain 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 illustrations, page 6-6. • If the dryer appears to operate correctly, 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. Measure exhaust temperatures with heater off and on. The correct exhaust temperatures are as follows: EXHAUST TEMPERATURES TEMPERATURE HEAT TURNS HEAT TURNS SWITCH OFF* ON SETTING °F (°C) °F (°C) High 155° ± 10° (68° ± 6°) Normal 145° ± 10° Medium, Casual (63° ± 6°) 10°-15° (6°-8°) Medium, Energy Saver 135° ± 10° below the (57° ± 6°) heat turn off Low 125° ± 10° temperature (52° ± 6°) Ex-Low 115° ± 10° (46° ± 6°) * 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) RES. kΩ TEMP. °F (°C) RES. kΩ 50° (10°) 19.0-22.0 80° (27°) 8.5-10.5 60° (16°) 14.8-16.8 90° (32°) 6.8-8.8 70° (21°) 11.5-13.5 100° (38°) 5.0-7.0 • If the thermistor resistance does not agree with table, replace the thermistor. • If the thermistor resistance checks agree with the measurements in the table, replace the electronic control assembly. 6-7

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6-7
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
HEAT TURNS
OFF*
°F
(°C)
HEAT TURNS
ON
°F
(°C)
High
155° ± 10°
(68° ± 6°)
10°–15° (6°–8°)
below the
heat turn off
temperature
Normal
145° ± 10°
(63° ± 6°)
Medium, Casual
Medium,
Energy Saver
135° ± 10°
(57° ± 6°)
Low
125° ± 10°
(52° ± 6°)
Ex-Low
115° ± 10°
(46° ± 6°)
*
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)
RES.
kΩ
TEMP.
°F (°C)
RES.
kΩ
50° (10°)
19.0–22.0
80° (27°)
8.5–10.5
60° (16°)
14.8–16.8
90° (32°)
6.8–8.8
70° (21°)
11.5–13.5
100° (38°)
5.0–7.0
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.
•
•