Just bought a used 1987 Real-Lite truck camper. The roof air unit is Dometic as well as the LP/AC refrigerator. When turned to "cool" the air conditioner really draws down, dims the lights, and eventually blows the home AC breakers. It works fine on blower fan only but as soon as I engage the "cool" settings, big brown out. The fridge doesn't work at all. I'm in the Nashville area. Suggestions

I would start there before replacing any parts. The circuit boards require 12volts to operate the refrigerator. If you have a good 12 volts and the LP tanks are full and the flame lights but the unit does not cool then you probably have a bad cooling unit. But start with the obvious issues first.

mud daubers will build dirt nests anywhere pull cover on roof see if drain stopped up

if the gasket is bad it could leak

Yes if its working properly. A 20 degree temp. differential between its supply air and return air its good.

Make and model of unit should be on base of roof assy, please reply with that so we can be sure we have right wiring info for you. Although they are pretty common, let's be sure.

its good to put them in, as it will keep dust from building up on the coils, thus reducing cooling.just buy some filter material at any hardware store, coarse, like a sponge, not fine paper stuff.

If it was start up capacitors, it wouldn't start initially every time. Do me/you, a favor, and remove your filter inside (return air) , and if it's a ducted system, remove entire plastic cover inside. Take a flashlight & look way up where filter covers in hole & take a good look at cooling fins on evaporator (front of AC). Look for restrictions such as dust etc. That dust will turn just like mud on there due to condensation mixing with dust, and block off flow which could cause unit to freeze up & compressor to kick out. If your real ambitious, and find lots of dust there, taking cover off roof unit would be next, and check same there at back end (condenser) coils & cooling fins.Get back to me after inspection from inside. Could still be electrical but lets check that it has proper maintenance & best chance to work properly by doing this first.

how old is unit and does it have refrigerant in it