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Replacement parts for MAYTAG MZD2665HEB REF - SXS/I&W | AppliancePartsPros.com

Have you tried unplugging the unit for 5 minutes or so.
Problem is you will have to to wait 24 hours to see if it does the trick.

The heater and the defrost thermostat check out OK so odds are that the defrost board (Item 12 in Section 4) is toast.

See the attachment for the tech sheet.
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I wonder if I can download the service manual for free anywhere for this refrigerator?[/COLOR]
I cannot find it at a free site but the tech sheet should help. It has info on how to force a defrost cycle..
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I will try unplugging it for 5 minutes....what does this do?[/COLOR]
If the board is hung up due to an electronic problem, this may clear that problem.

[COLOR="DarkRed"]Can we test the ADC[/COLOR]
Not really but we can use it to check other components.
If a forced defrost turns the heater on then we know that the heater, the defrost thermostat and the wiring are OK.Since the only component left in the circuit is the adaptive defrost board we would replace it as it will not start a defrost cycle on it's own.
Note: The defrost thermostat must be frozen when you do the check as it opens and kills power to the heater just above freezing.

Note 2: If the heater does not come on, it does not eliminate the defrost board as the problem so we then check the heater and thermostat for continuity. If they measure OK, we then replace the defrost board. It is a bit of an assumption that the wiring is OK but problems with it are very rare.