Manitowoc Q450 Service Technician's Handbook page 65

Step 3. Disconnect the ice thickness probe from the
control board at terminal 1C. Clip the jumper wire
leads to terminal 1C on the control board and any
cabinet ground.
Monitor the Harvest light.
Harvest Light On
• The harvest light comes on, and 6-10 seconds later,
the ice machine cycles from Freeze to Harvest.
The ice thickness probe is causing the malfunction.
• The Harvest light comes on, but the ice machine
stays in the Freeze sequence.
The control circuitry is functioning properly. The ice
machine is in a six-minute freeze time lock-in (verify
step 1 of this procedure was followed correctly).
Harvest Light Off
• The Harvest light does not come on.
The control board is causing the malfunction.
ICE MACHINE CYCLES INTO HARVEST BEFORE
WATER CONTACT WITH THE ICE THICKNESS
PROBE
Step 1. Bypass the freeze time lock-in feature by
moving the ICE/OFF/CLEAN switch to OFF and back
to ICE. Wait until the water starts to flow over the
evaporator, then monitor the Harvest light.
Step 2. Disconnect the ice thickness probe from the
control board at terminal 1C
• The Harvest light stays off, and the ice machine
remains in the Freeze sequence.
The ice thickness probe is causing the malfunction.
Verify that the ice thickness probe is adjusted correctly
and clean.
• The Harvest light comes on, and 6-10 seconds later,
the ice machine cycles from Freeze to Harvest.
The control board is causing the malfunction.
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