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Sunday, January 23, 2011

RV Roof Air Conditioner Caused No-Voltage Situation

I recently purchased a 2008 Lexington. I started the generator and after a few moments I turned on the air conditioning unit. While adjusting the thermostat on the air conditioner I accidentally turned it off. I turned the air conditioner back on and immediately I lost the electrical power. Not only power to the air conditioner, but also power to all my 120-volt circuits (TV, microwave, etc). I went to the bath and tried to reset the GFCI. It would not reset. We went to an RV park a half an hour later and I thought the shore power would do the trick. However, in a nutshell, while the generator is running or when I have shore power, I cannot get any 120-volt circuit operating. I did not trip a breaker on my panel box, however I reset all those as well. Where else might a breaker be? Help! Charlie, (Hampton, VA) 

Charlie, your Lexington incorporates an automatic transfer switch to facilitate the automatic switching between the voltage from the generator and the shore power. I realize you’ve reset the circuit breakers on the main panelboard, but also make sure the circuit breaker on the generator itself is not tripped. If that breaker is tripped, and at the same time, the transfer switch relay is stuck on the generator output, you’ll not have any voltage coming in from the shoreline. However, it sounds like the power surge caused by the accidental short cycling of the A/C compressor probably blew the fuse inside the transfer switch or possibly damaged the relays inside. You are apparently not receiving voltage from either source now as evidenced by the GFCI. The coach GFCI will only “test” when voltage is applied to that circuit. You’ll need to locate the auto transfer switch box.

The transfer switch is a large box usually relatively easy to find since the shore power cord feeds directly into it. Trace the shore power cord as it enters the motorhome and you should find it. It may be behind another piece of gear. It will most likely have two other power cables leading to it; from the generator and the converter. 

Once you locate the transfer switch, make sure the shore power cable is unplugged and the generator is not running. Open the transfer switch cover and check the fuse(s) inside. If a fuse is blown, replace it. If not, there could be internal damage to the switch controls and/or the associated relay and you will need to have your system diagnosed professionally. You should have no trouble replacing the fuse, but a Certified RV technician should only attempt further internal diagnostics.

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