I assume we are talking about electric strip heaters in the AC units? The front ac unit is 1300 btu and the rear is 1100 btu on factory systems. Which means the front ac should have a 20 amp breaker and the rear unit a 15 amp breaker. The electric heaters are probibly 1500 btu each? If this is the case there is a good chance you are pretty close to 15 amps draw on each unit figuring the motor and strip heater. This would likely trip the 15 amp breaker after a short time . Do you have access to an amprobe to check the actual amp draw on the rear unit. If it is less then 15 amps tightening the connections as Emery suggested would help or the breaker could be failing .Is the breaker getting hot before it trips? Like I say you need to know the amp draw of the rear unit to determine if you are at the breakers current limit.

My grandmother who passed away some forty years ago told me about the year in North Dakota when the kerosene froze. I looked it up. Kerosene freezes at 65 degrees below zero. This winter which is still six weeks away looks to be a cold one. I'm hoping to be ready for when the kerosine freezes.

My new furnace finally works (long story last year about my furnace from hell- heck, you think that would keep you warm, but I digress). However, I spend $20 a week for propane but two space heaters and two warming elements in my a/c units have kept me warm and dry until now when the temps have plummeted. Electricity in the Northwest is a lot cheaper than propane.

Enough BS. My issue is that my rear a/c unit trips a breaker after an hour or so of normal operation. My forward a/c unit chugs along, warming the forward part of my coach quite nicely. I'm an electrical idiot. Is there something else on the rear circuit that draws more current than the forward a/c unit? Perhaps it is simply a variation in construction of my Duotherm, Briskair units. You guys always have an insight. Let's hear it guys.