After six weeks of troubleshooting my Dometic DMC4101, replacing the freezer evaporator fan, fan-control board, and rear PCB/power module, I finally identified what appears to be the problem.
Symptoms:
The refrigerator's main 12V supply remained above 13V during the failure.
My voltage measurements at CN3 during failure:
| Measurement | Result |
|---|---|
| CN3 red to FGND (black) | 0V |
| CN3 red to refrigerator ground | 13V |
| CN3 black (FGND) to refrigerator ground | Approximately 13V |
During normal operation, CN3 red to black (FGND) measures over 13V.
When the failure occurs, that reading drops to approximately 0V.
What I discovered:
The red wire retains positive voltage, but the FGND connection rises to approximately the same voltage. This is consistent with the fan losing its ground return.
I found no visible burn marks on the PCB.
I connected an additional ground wire between FGND and the refrigerator's main ground. The refrigerator resumed operation immediately without requiring a power reset.
I have not identified the exact failed electronic component. I also have not established whether this bypass is safe for long-term use or whether it defeats a protective function.
I'm sharing these measurements because they may help others diagnose the same issue before purchasing multiple replacement parts.
Important: This is a report of my troubleshooting results, not a verified manufacturer-approved repair. The bypass should be evaluated for electrical and operational safety before being used permanently.
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