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Old 08-26-2016, 08:50 PM   #1
wvphil's Avatar
Join Date: Sep 2014
Posts: 73
12 volt source and fuse for front ac control

The dometic ac's have 12 v sent from somewhere up to the area of the ac where control box is located in ac. This 12 volts is used to supply voltage back to the wall thermostat and to power the control box located in the ac under the removable filter inside the coach. Anyone know where this + 12 volts and ground wire ie - 12 volts as labeled on wires from control box come from and where it is fused? I do not see any listing in the 12 volt side of the breaker box for ac control. Ive had some stange problems this past week with front ac. When unit reaches set temperature unit kicks off as expected. However had several repeat incidents where ac did not kick back on once temperature rose above set point ( not even after say five degrees). When this happened if i did a reset on thermostat by holding the + temp button and mode button for three seconds then received the -- on display as expected then pushed mode button till back to cool the unit would turn back on. I suspected a bad control box and replaced it along with a new thermostat and temp probe included in the new kit but experienced same problem. (Only with front ac rear worked without issues) of corse rear has its own thermostat and control box. So here is where the story gets interesting. I experience this for approx four days this week while in tenn on vacation. Today when I leave I ran both ac's on generator for approx five hours on return trip home and the front ac has worked without problems. Ive been home for around six hours and have plugged the coach into my garage power and have run the ac since arriving home. It is cycling as it should and will turn off when i increase temperature and will cycle back on when i decrease thermostat. ( after compressor timeout delay of a couple minutes) as expected. I want to think it could of been the power at the campground but do not find that logical since the rear ac worked fine all week. Id like to know where the 12 volts and -12 volts originate so i can inspect for a possible loose or corroded connection. Any info would be appreciated. Now the next post is my last question. Sorry so many questions tonight.

2013 Georgetown 378 XL
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Old 08-27-2016, 04:44 PM   #2
Tim & Lisa Trempert
Join Date: Sep 2008
Posts: 397
I'm not an electrical expert, but I think each AC runs on a separate phase of the 50amp at the campground so it is entirely possible it was the campground circuit either dropping, a bad breaker (one side of the two pole breaker) or brown outs.

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Tim & Lisa
2011 Georgetown 350
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12 volt, fuse

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