GE PSH23PGR Series, Technical Service Manual

Page: 19 / 62

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Fresh Food Evaporator Thermistor
The fresh food evaporator thermistor (part #
WR55X10025) is located in an aluminum thermal
block on the back of the evaporator. It is attached
to the fresh food evaporator by a wire tie. See
Fresh Food Evaporator
for accessing instructions.
If the fresh food evaporator thermistor is either
open or shorted, the main control board defaults
to a fi xed defrost cycle of 1 hour at high speed
fan.
Thermal Block
Barbs on the molded housing hold the thermistor
in the thermal block.
Replacement
Should the evaporator thermistor require
replacement, splice a new thermistor into the
harness using plastic bell connectors (part #
WR01X10466). Fill the connector with RTV102
silicone as shown in the illustration.
Barbs
Thermistor
Fresh Food Evaporator Fan
A variable speed
12 VDC motor
is mounted in
front of the fresh
food evaporator.
The fan and
evaporator cover
are replaced
as a complete
assembly.
When activated, the fresh food evaporator fan
recirculates the air in the fresh food compartment,
providing cooling independent of the freezer
evaporator fan.
The main control board gathers information from
the fresh food thermistors to determine when, and
at what speed, fan operation should occur.
A constant 13.6 VDC is provided to the fan from
the main control board and switching occurs on
the neutral side.
Speed is regulated by pulse width modulation on
the common side of the fan. When operating, the
common side of the circuit is pulsed open and
closed. This pulsing produces effective voltage
being received at the motor, which is equivalent to
a reduction in voltage. Fan speed is selected and
maintained by the main control board regulating
the length and frequency of the 13.6 VDC pulse.
High Speed (12 VDC measured)
Medium Speed (10 VDC measured)
Low Speed (9 VDC measured)
12 VDC
10 VDC
9 VDC
13.6 VDC
0 VDC
0 VDC
0 VDC
13.6 VDC
13.6 VDC
Insert the new thermistor into the thermal block.
Add RTV102 silicone to hold the thermistor in
place. Make certain to wire tie the thermal block
back to the evaporator.