Dometic RM100 electric thermostat problem

[blickcd]

The refrigerator used to run fine on electricty. When I turned it on last Wednesday to cool down for a weekend trip, with the thermostat set on 4, the fridge cooled down to the high end of the "safe" range on my fridge thermometer.

Pardon me for not knowing that actural temperature off hand but a setting of 4 normally puts the temperature right in the middle of the safe range, which is I think about a 10 degree spread. That was after cooling down overnight, ambient temperature in the mid 60's.

I turned the thermostat up another notch and checked it maybe 8 hours later in the day, ambient temp now up to the high 70's. Fridge temp had not budged.

Turned it up another notch, now at 6, still no response but we used it anyway for a great weekend at a local state park. Durning that weekend, day and night temps about the same as described before, and our site having less shade than where the trailer is normally parked at home, the fridge temp dropped about 5 degrees. That's to the middle of the safe range, and the temperature I would expect to see with the thermostat set on 4, not 6 which is where it was.

I know that was a lengthy explanation but is this a sign that the electric thermostat is going bad or the heating element is going bad? It looks like both are easily replaced from the outside without removing the fridge. Correct?

Thanks,
Christopher