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.
September 2006 Page 67
Test Procedures - Loads
