Rear AC won’t turn on after I change selector to rear AC

[Geocritter]

I just purchased a 1994 33’ Holiday Rambler RV. It’s a fixer-upper and I’m hard at it setting the old gurl right. I’ve worked over 3 fixer-upper power boats so I’m not a complete virgin at this sort of thing. Unfortunately, though I’m very handy, there are some systems that I’m a bit inexperienced working on, hence my question about my RV’s 2 AC units.
The rig has a 30 amp system and as I understand it, you can only run one of the roof top AC’s at a time, unless you’re running on generator power. However, you can run both AC’s at once using the onboard generator. Here’s the problem:
When hooked up to an AC power source (my house), the front AC works fine. However, when you switch to rear AC only (using the selector switch) the rear AC won’t turn on.
However, both AC’s will turn on and run if their power is from the onboard generator (so I suspect the problem isn’t in the AC).
I’m guessing the problem is in the selector switch, though it appeared to work fine with the generator power. Before I tear into things, has anyone here had a similar problem and if so what caused it?
Thanks in advance for any insight given to solving this mystery.
Steve

[Geocritter]

I'd like to give my thanks to all those who responded to my questions regarding my rear AC unit. I haven't fixed it yet but I ordered some 1998 vintage repair manuals through Abebooks.com. I'm hoping that when I get the manuals, and with the suggestions offered up in this thread, I'll soon get the rear AC running.
Steve

[MrDoneIt65]

I experienced this problem shortly after I bought the Southwind. Turned out to be interference from the converter, which was located under my refrigerator and the control unit for the air conditioners. Had to change the converter to a better model. I also had a problem with my front air conditioner icing up and it burned out the compressor. Turned out that when Fleetwood installed it they did not untape the probe and put it in the coils like they were suppose to do. I bought a new, 15,000 btu conditioner and put it on the roof myself. I put a ladder up against the end of the motor home, disconnected the burned up unit, tied a rope to it and let it down the ladder. Then I tied the rope to the new unit, pulled it up the ladder, carried it down to the opening, hooked it up, I have more cold air than I ever had from the OEM. And Fleetwood didn't give a dang.

[Jay58]

Google. ..... pulse air. It's a relay system that runs front for 10 minutes then rear 10 minutes then it goes 7 and 7 for the rest of the time it's running and this is on a 30 amp service.. I had it on our Winnie.

[Don_Don]

BillMFl wrote:
Check the 110vac circuit breakers. There should be one for each air conditioner. If they are good to go check voltage from each switch position.

If the breaker was tripped it would not work at all.

[John_Wayne]

Will the rear one work on shore power with the front one off. If so I'd say it's the power management system. As it will let both run when on generator power. It may also be that of the 2 breakers on the generator one may be just for the rear air. Turn the generator breakers off one at a time and see if the rear air goes off.
Just make sure you wait a few min.s before you reset the breaker if the AC is still on it needs time to bleed off the head pressure.

[Mandalay_Parr]

Probably not the selector switch. You may have a power management system that is keeping the rear one from working.

[BillMFl]

Check the 110vac circuit breakers. There should be one for each air conditioner. If they are good to go check voltage from each switch position.