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Son_of_Norway's avatar
Son_of_Norway
Explorer
Jun 28, 2017

Wiring a separate plug for the rear AC Part 2

My RV only has 30-amp power and can only run one AC at a time while on shore power. I made a post awhile back about wiring in a switch and a separate plug in the generator compartment so I can run my rear AC. The consensus was that I needed to identify the circuit that went back to the rear AC. I'm not having any luck doing that so I hope that I can get some more advice.

I separated out the wires for the house wiring that went to the generator compartment: 2 black wires, and and I separated the 2 white wires that were tied together. (I just left the grounds connected to the box.) First I tried to figure it out by testing continuity. I tried each of the four possible combinations of black and white wires but none had continuity with the wires at the rear AC.

Then I decided that maybe the circuit had to be energized in order to figure it out. So I plugged into an AC outlet and energized each of the four combinations one at a time. I couldn't get any power at either the rear AC or the house circuit with any of the combinations.

I checked for power by plugging in the coach AC cable and there was power. So what am I missing and how can I find out which wires go back to the rear AC?

Thanks for your help
  • pianotuna's avatar
    pianotuna
    Nomad III
    Jun 28, 2017
    I hope you kept photos of the OEM wiring.

    Put it back the way it was.

    Now try the rear AC.

    Does the rear air work?

    If yes, then set the rear air to fan only.

    Then flip the breakers off (then on) one by one.

    Leaving that breaker off, does the front air now run?
  • time2roll's avatar
    time2roll
    Nomad
    Jun 28, 2017
    I thought some of these generators powered the second A/C direct.
    One hot to feed the main panel and the other to feed the second air.

    Does the second air only run when using the generator?
  • Dutch_12078's avatar
    Dutch_12078
    Explorer II
    Jun 28, 2017
    Do you have a selector switch that chooses which A/C you can run on shorepower? Below is a block diagram showing how our previous 30 amp coach was wired with two A/C's. It also shows where I added a plug and socket that allowed running both A/C's on 30 amp shorepower using an extension cord and the 20 amp outlet in the shorepower box.


    Click For Full-Size Image.
  • jvowell1's avatar
    jvowell1
    Explorer
    Jun 28, 2017
    I did my 1996 Damon intruder last summer. From the generator I have 2 120 volt circuits, neither went directly to the rear air. I went behind my power converter and found the wire that went to the rear air. I cut the wire and then ran wire from each side of those wires to one of my bays. I put heavy duty plugs on the ends. When I need to run the rear air I unplug the wires and plug an extension cord to the end going to the ac. When I run the generator I just plug the wires back together to complete the circuit like original. Hope this helps
  • Son_of_Norway's avatar
    Son_of_Norway
    Explorer
    Jun 28, 2017
    Thanks to all. I am trying to think this through. There is a switch in the coach to choose between the front and the rear AC. I think I'll put the wiring back as it was and use a clamp-on meter to see which pair of wires the rear AC draws from.
  • Bobbo's avatar
    Bobbo
    Explorer II
    Jun 28, 2017
    Son of Norway wrote:
    Thanks to all. I am trying to think this through. There is a switch in the coach to choose between the front and the rear AC. I think I'll put the wiring back as it was and use a clamp-on meter to see which pair of wires the rear AC draws from.

    This statement shows that they have a single, common, wiring pair that feeds them up to the switch. The switch is where they branch off. If you want to run another power cord to the rear A/C, the wiring at the switch is where you will have to tie in.
  • Dutch_12078's avatar
    Dutch_12078
    Explorer II
    Jun 28, 2017
    On my previous coach, I cut in the new socket and plug for the front A/C in my case, at the generator wiring junction box. As you can see on my block diagram, the selector switch had to be in the "Rear" position to run both A/C's on either the generator or using the new extension cord setup to run the front A/C.

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