[JRTJH]

It sounds like you've got a bad thermistor, but before you change it, one "trick" you might try is to remove the thermistor from the fin, clean it by sliding a piece of paper through the slot and then move it over to the left a couple of fins. That may do the trick, if not, move it a couple more fins. If that will work, it'll do it by about 6 or 8 fins. If not, then you need to replace the thermistor. That's a simple change using the existing wires and connecting a new thermistor. There is a "replacement kit" available from an aftermarket company that includes a "rotary knob" thermostat that you can set. I don't have any experience with that kit, but have heard "good things" about it. Personally, I'd try moving the thermistor, if that doesn't work, then getting a Dometic replacement.

Good Luck