GE PSH23PGR Series, Technical Service Manual

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The evaporator fan is the same fan used on
previous models; however, a signifi cant difference
is that the main control board neither requires
nor receives input from the fan feedback/rpm
(blue) wire. The fan utilizes a permanent magnet,
4 pole, DC motor that operates at three different
speeds: high, medium, and low.
The speed of the fan is controlled by the voltage
output from the main control board. Voltage
output from the main control board to the fan
is 13.6 VDC; however, to regulate the speed of
the fan, the main control board uses pulse width
modulation (PWM).
When operating, voltage is sent in pulses (much
like a duty cycle) as opposed to an uninterrupted
fl ow. This pulsing of 13.6 VDC produces effective
voltage being received at the motor, which is
equivalent to a reduction in voltage.
Freezer Evaporator Fan
The position of the fan blade in relation to the
shroud is important.
5/16" ± 0.03
Blade tip
1.0" ± 0.05 Target
Motor
Air Flow
Orifice
Fan speed is selected and maintained by the
main control board regulating the length and
frequency of the 13.6 VDC pulse. Temperature
can cause some fan speed variation. Fan speed
can vary +/- 5%, depending on the temperature,
with higher temperatures causing slightly higher
speeds.
The evaporator fan has a 4-wire connection:
White Wire (DC Common)
The white wire is the DC common wire used
for testing. During repairs, DC polarity must be
observed. Reversing the DC polarity causes a
shorted motor and/or board.
Red Wire (Supply)
Each motor uses an internal electronic controller
to operate the motor. Supply voltage from
the main control board remains at a constant
13.6 VDC.
Blue Wire (Feedback/RPM)
On previous Arctica models, the blue wire
reported rpm (speed) information to the main
control board for speed control purposes. On this
model, the board does not require or read any
feedback information from the fan motor.
Yellow Wire (Signal)
The yellow wire is the input wire from the main
control board. The main control board provides
6.5 VDC effective voltage for low speed, 8 VDC
effective voltage for medium speed, and 9.5 VDC
effective voltage for high speed. The fan operates
in low speed only when the fresh food thermistor
is satisfi ed.
Note: When testing these motors:
• You cannot test with an ohmmeter.
• DC common is not AC common.
• Verify 2 voltage potentials:
a. Red to white - power for internal controller
b. Yellow to white - power for fan
• Observe circuit polarity.
• Motors can be run for short periods using a
9 volt battery. Connect the white wire to the
negative (-) battery terminal only. Connect
the red and yellow wires to the positive (+)
battery terminal.
High Speed (9.5 VDC measured)
Medium Speed (8 VDC measured)
Low Speed (6.5 VDC measured)
9.5 VDC
8 VDC
6.5 VDC
13.6 VDC
0 VDC
0 VDC
0 VDC
13.6 VDC
13.6 VDC