In my experience, the control board on Manitowoc Ice Makers is quite possibly the #1 misdiagnosed component.  Service technicians tend to blame the electronics in the control board before properly testing and checking on the various probes that tell the board what to do.  Remember, garbage in, garbage out.

Before ordering or replacing a Manitowoc control board, check the following probes.

Water Level Probe – Often times when the water level probe gets dirty from scale build up, it will false read, telling the control board that the sump trough is full.  Because the board is being told the trough is full of water, it will shut the water inlet valve off.  This will lead to thin or no ice formation on the evaporator.

S Series Manitowoc Water Level Probe 20-0654-9

Q Series and older Manitowoc Water Level Probe 25-1129-3

Ice Thickness Probe – The ice thickness probe on Manitowoc Ice Machines is another common item that will fail due to being dirty.  The scale build up from hard water will tell the ice machine that it’s got a full sheet of ice and ready to harvest, when in reality there may be little to no ice formation.  Early harvests, with no ice to trip the bin switch, will eventually lead to a safety limit lock out.  Clean or replace your ice thickness probe before replacing a control board, your bottom line will appreciate it.

S Series Ice Thickness Probe 20-0802-9

Q Series and Older Manitowoc Ice Thickness Probe 76-2781-3

Magnetic Bin Switch – The bin switch on Manitowoc Ice Makers is the component that tells the machine when the ice has harvested off of the evaporator.  When the ice falls it will break the magnetic proximity switch on the water curtain, which tells the ice machine to terminate the harvest sequence and go back into a freeze cycle.  This item can be very difficult to diagnose because of being an intermittent problem, the only way to test is to OHM the switch out and look for consistency.

S Series Magnetic Bin Switch 000007888

Q Series and older Manitowoc Magnetic Bin Switch 23-0148-3

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