I could not find a manual for a fridge that old online on any of Dometic's sites.
You can email them at email@example.com
and they may be able to help you.
FWIW, on most of Dometic's fridges that use a 12vdc control circuit board, the thermistor would be one likely cause of your problem. It is a probe that is inside the fridge itself, and is connected to the circuit board by two wires. You may be able to obtain a replacement through Dometic or an RV dealer.
If there is a 12vdc circuit board, the other likely cause would be a bad circuit board.
In the files area under Kitchens, there is a file for troubleshooting some models of Dometic fridges. These are the primary two causes of freezing.
'12 F250 4x4 Super Duty PowerStroke 6.7 diesel
2011 to present: '11 Cougar 326MKS
1999 to 2011: '99 Sunline T-2453
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