GE GFDN240, Technical Service Manual, Page: 42 / 53

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Inlet Safety Thermostat
On electric models, the inlet safety thermostat is
located on the top left area of the heater housing,
to the left of the inlet control thermistor. On gas
models, the inlet safety thermostat is located on
the right side of the diffuser, above the inlet control
thermistor. The thermostat monitors incoming air
temperature.
If the thermostat reaches a temperature beyond its
maximum temperature rating, it will trip and disable
power to the heating elements (electric models) or
burner assembly (gas models).
On electric dryers, the inlet safety thermostat opens
at 210°F (99°C) and will automatically reset at 180°F
(82°C). On gas dryers, the inlet safety thermostat
opens at 300°F (149°C) and will automatically reset
at 260°F (127°C).
To remove the inlet safety thermostat:
1. Remove the drum. (See
Drum
.)
2. Disconnect the 2 wires from the inlet safety
thermostat.
3. Remove the Phillips-head screw that attaches
the inlet safety thermostat to the heater
assembly or diffuser.
4. Lift and slide the thermostat from the heater
assembly or diffuser.
Inlet Control Thermistor
On electric models, the inlet control thermistor is
located on the top left area of the heater housing,
to the right of the inlet safety thermostat. On gas
models, the inlet control thermistor is located on
the right side of the diffuser, below the inlet safety
thermostat. The thermistor monitors incoming
air temperature and will respond to temperature
changes of 3°F. The thermistor relays this
information to the control board.
The thermistor has a negative coef fi cient. As the
temperature increases, the thermistor's resistance
decreases.
Electric Model Shown
Inlet Safety
Thermostat
Thermistor Resistance Values
Temperature
°C
Temperature
°F
Resistance
K-Ohms
10 50 202
16 60 151
21 70 120
25 77 100
32 90 74
38 100 57
49 120 37
57 135 27
66 150 19
93 200 8
121 250 3
(Continued Next Page)
Note: If the control reads a thermistor value too
high or too low, it will log an error code and switch
to a setting where the heaters are on a duty cycle.
The dryer then relies on the backup thermostats to
control the heater and will go into fall back mode
when it has determined that it can no longer rely on
the thermistor temperature to control the applied
heat. This occurs when a thermistor cannot sense
heat (failed open) or reads hot (failed closed). The
fall back mode consists of reducing the maximum
heating power (typically 50%) so that thermostats
are fast enough to shut down the heater in case of
overheating. On GE dryers, both heaters are cycled
on and off every minute.
Operation of the inlet control thermistor can be
checked by using service test mode T06. (See
Service
Test Mode
.)
Speci fi c failures associated with the inlet control
thermistor can initiate error codes E3 and E4. (See
Service Test Mode
.)