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  1. #1
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    12 V supply to rear thermostat

    I have recently added a second roof air, as mine only had one when purchased. I have found and connected to all the appropriate wiring, with exception of the 12 volt that supplies the thermostat. Why? Because I can't find it and it is nowhere in any wiring diagrams I have been able to find. Which is not many. There is a orange and orange white pair in ceiling. I have tested this line and it doesn't have any power to it. Any suggestions? Your help would be greatly appreciated. Thanks.

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    Seasoned Camper
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    Quote Originally Posted by Metalviz View Post
    I have recently added a second roof air, as mine only had one when purchased. I have found and connected to all the appropriate wiring, with exception of the 12 volt that supplies the thermostat. Why? Because I can't find it and it is nowhere in any wiring diagrams I have been able to find. Which is not many. There is a orange and orange white pair in ceiling. I have tested this line and it doesn't have any power to it. Any suggestions? Your help would be greatly appreciated. Thanks.
    I picked up 12 vdc from the hallway motion light.

  3. #3
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    Was your trailer not framed and prewired for a second AC?
    2010 Jayco 26(SOLD)
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  4. #4
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    Quote Originally Posted by Metalviz View Post
    I have recently added a second roof air, as mine only had one when purchased. I have found and connected to all the appropriate wiring, with exception of the 12 volt that supplies the thermostat. Why? Because I can't find it and it is nowhere in any wiring diagrams I have been able to find. Which is not many. There is a orange and orange white pair in ceiling. I have tested this line and it doesn't have any power to it. Any suggestions? Your help would be greatly appreciated. Thanks.
    It seems to me that the Orange and the Orange/White pair that you found should be the 12VDC. If you have checked them and do not have power there, take a look in the 12VDC fuse panel, which is located inside the 120VAC breaker panel on most units. If there is labeling, and there should be, see if you have anything related to A/C control or something similar and check that fuse..
    2016 F350 CrewCab Dually
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    Excessive Payload is a Wonderful Thing

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  5. #5
    Seasoned Camper
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    Quote Originally Posted by BobLandry View Post
    Was your trailer not framed and prewired for a second AC?
    Only for 120 vac. No 12 vdc there.

  6. #6
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    12 V Success

    Quote Originally Posted by xrated View Post
    It seems to me that the Orange and the Orange/White pair that you found should be the 12VDC. If you have checked them and do not have power there, take a look in the 12VDC fuse panel, which is located inside the 120VAC breaker panel on most units. If there is labeling, and there should be, see if you have anything related to A/C control or something similar and check that fuse..
    The Orange and Orange/White pair that are in the ceiling IS the 12V supply. I learned not to trust my fancy multimeter. After numerous tests with the high dollar one, I tried with my cheap "light tester" and Shazam! We have power. I do appreciate everyone's input. I feel a bit behind the curve, when it comes to brain function at the moment. Unit is up and running and working wonderful!!!

  7. #7
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    Quote Originally Posted by Metalviz View Post
    The Orange and Orange/White pair that are in the ceiling IS the 12V supply. I learned not to trust my fancy multimeter. After numerous tests with the high dollar one, I tried with my cheap "light tester" and Shazam! We have power. I do appreciate everyone's input. I feel a bit behind the curve, when it comes to brain function at the moment. Unit is up and running and working wonderful!!!
    That is great news......well, except that your multi-meter failed you. Before you do anything rash with it, like toss it in the trash....just make sure that you had it on the correct settings. I had one years ago that the leads were the problem of why it wasn't working. I had a lead on the meter that the conductor/wire inside the lead itself had broken. You couldn't see it though because of the insulation. The way I found it was to "pull" gently on the lead, along the whole length of the lead. I found a place on it that would "stretch" a little bit, as compared to the rest of the lead. I bought a new set of leads and I still have that meter and it works fine. Obviously if the leads are not the type that plug into the meter, then it's a different story. Anyway, glad you got the A/C unit running and glad I could help.
    2016 F350 CrewCab Dually
    2018 Momentum 394M....Got it!
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    Excessive Payload is a Wonderful Thing

    "If it ain't fast....It ain't Fun"

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