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Friday, October 23, 2009

Two A/C Dilemma

I have a Fleetwood Southwind with two air conditioning units. They are on a front/rear switch so you can only use one unit at a time. The rear one works great but if you turn the switch to front nothing happens. They both worked last week and I haven’t done anything except take it to have the oil changed and an alternator replaced. My question is other than the main panel is there another set of breakers or fuses on the unit? With the generator on and the rear air going if I turn off the A/C breaker, nothing happens; in other words the rear A/C unit keeps going. The front unit will not even turn on now so I am really puzzled. Any ideas?
Phillip, (Berea, KY)


I know it may appear slightly confusing, Phillip, but there is a logical explanation. Your Southwind was wired for two installed roof air conditioners, but because the shoreline cord is only rated for 30-amps, you are only able to run one roof A/C at a time. Remember each air conditioner must be on its own 20-amp circuit. That “either/or” (front/rear) switch lets you choose which air conditioner to run while plugged into shoreline power. Running both units off the shoreline, as equipped from the factory, is mathematically and electrically not possible; hence the need for the “either/or” switch. 

The generator adds another factor into the mix. It is rated to power both roof air conditioners at the same time…it has enough output capacity. Typically, the rear air conditioner is hard-wired directly to the generator output. On the side of the control box on the generator, you’ll find two, push-button circuit breakers, one is wired directly to the rear roof A/C, (that’s why the rear unit runs with the generator operating), and the other breaker is wired to the coach distribution panelboard which protects all the 120-volt circuits in the coach, including that front A/C. 

Chances are, given your symptoms, the front air conditioner breaker in the panelboard distribution box is faulty, the “either/or” switch is faulty or there could be a problem with the wiring to the front roof A/C. There is also an outside chance a problem in the front air conditioner could exist as well. 

A few simple continuity measurements with a volt-ohmmeter will clear up the mystery. If there is continuity through the “either/or” switch from the panelboard breaker to the front A/C then the problem lies in the air conditioner itself. If there is a break in the continuity anywhere between the breaker and air conditioner, it would implicate either the circuit breaker itself, the “either/or” switch or a wiring connection somewhere in between. A competent RV tech should find where the problem lies in about an hour’s time. The repair, however, make take longer depending the actual cause of the symptoms.

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