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MC0322 through MC2148
Air, Water, and Remote Cooled Service Manual
Test Procedures - Pressure switches
There are two pressure switches: Fan and High Pressure cut out.
Fan. The fan pressure switch will open to shut the fan motor off at a certain pressure and re-close at a preset
higher pressure.
High pressure cut out. The high pressure cut out switch will open at a preset pressure, shutting off power to
the compressor contactor. After the pressure has fallen to another preset level, the switch will re-close and the
contactor coil will be engergized.
To Test Fan Pressure Switch:
A. Attach refrigeration gauge set to high side port.
B. Unplug both wires from fan pressure control. Be SURE the wire's terminals are wrapped in electrical tape to
prevent short circuits to ground during the test.
C. Connect ohmmeter to terminals of fan pressure control..
D. Switch ice machine on, observe pressure that the pressure control closes at, compare to spec. Switch unit
off, allow system to equalize, observe pressure the pressure control opens at, compare to spec.
To Test High Pressure Switch:
A. Attach refrigeration gauge set to high side port.
B. Unplug fan motor or shut water off if water cooled.
C. Measure voltage between contactor side terminal of high pressure control and ground.
D. Switch ice machine on, observe pressure that the pressure control opens at, compare to spec. Allow system
to equalize, observe the pressure that the pressure control closes at, compare to spec.
Transformer
Check secondary voltage, it must be between 10 and 15.5 AC volts. Replace if no voltage is output or if above
or below the acceptable voltage..
Controller
The controller's software operation is confirmed if it is functioning. Execute the test to confirm its operation of
the loads. Illumination of a diagnostic code (other than E) is not an indication of controller failure. Each code
requires its own diagnosis.
January 2022
Page 55
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