2000 monaco diplomat cabin gets hot going down road?

[mmraceca]

I have a 2000 Monaco diplomat that has two a/c units that work great setting still. Once going down the road it seems to suck the cool air out or just get hot. I have tried running and not running the dash air. As soon as we get where we are going or stop for fuel/food, it cools back down. I have all the vents closed and the slide is sealed good. Thanks, Justin

[Gary RVRoamer]

Sounds like the air vent door may be stuck open, bringing warm outside air in. I also had a coach once that had a fairly large hole in the firewall that was wide open. About 1" in diameter and it let in a lot of hot (or cold) air at highway speeds. Fixed it with a squirt of polyurethane foam, e.g. Great Stuff.

[Sixpack98]

Don't know if you have the same Frigatte AC/heater assembly as my '06 Endeavor but I had a defective vacuum hose that allowed the hot water to flow through the heater core which kept the front very warm underway. May check to see if the vacuum operated heater valve is closing.

[mahon1993]

Ok, so you are running the generator and using both AC's while traveling, right??
Check the vent on the firewall in front of the passenger seat to see if hot air is blowing in while moving. I don't know what floor plan you have but on mine, 40BPD, I put a latch on the sliding door going to the bath/bed room to block out the heat from the engine and just use the front AC. There is a tremendos [sp] amount of heat that comes from the engine.
Greg