Hi,
Please tell us the model of the fridge. Look inside the fridge compartment, and there should be a label with the model number on the sidewall. Sunline used Dometic for the fridges; please let us know if it is still the same brand or has been changed.
Also, remove the outside lower vent of the fridge, which exposes the back side of the fridge, including the gas lines, gas burner, and limited electric controls. Take and post a few pics of the back of the fridge as seen with the lower vent removed. We can then see what you have and may be able to point out what to look for. The electric element and the switch to turn it on/off are in this area, assuming you still have the old-style fridge that came with the camper in 1989.
I hope this helps,
John