98 Palomino Mustang 8 pin plug to 7 blade questions

Discussion in 'Wiring' started by Matt D Bushnell, Jun 29, 2020 at 12:42 PM.

  1. Matt D Bushnell

    Matt D Bushnell New Member

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    Apr 15, 2020
    Hello All,
    I am new to the popup camper world. Growing up my parents had a truck camper and later a pull trailer and I never had to worry about if things worked or not. But now, being an adult with my own family I need some help. We have used tents until recently buying an old popup which needed some work.
    I have completed most of the canvas work and now replaced the roof with a new rubber cover and am doing the electrical. I am pretty good with wiring things up when standard wires are available. But with this PU it has a 8 pin rectangular hookup so I cut the wires and started converting it to a 7 blade adapter since my GMC has a 7 blade receptacle.
    I think I have it figured out as far as running lights, turn signals, brake lights and so forth.
    The wires are from top left to right
    Blue 14 G (Trailer brakes - which this trailer does not have) - Green 14 G (Running lights) - Black 14 G (Pig tailed - one to trailer one to PU battery positive terminal and 12v + for interior lights) - White 12 gauge (Battery Negative terminal)
    The second row of wires from left to right are
    White 14 G (To PU chassis ground) - Brown 14 G (right turn) - Red 14 G (Left turn) - Grey 14 G (Unknown where to connect this to).

    If you see something wrong with the wiring please reach out and let me know so I do not fry anything.

    So here are my questions...
    1. Out of the 8 wires there were 2 white ground wires. One for the PU frame ground and one for the PU battery ground terminal. But which one is which? Maybe since going to a 7 blade I just hook them both to the same ground and then pigtail them to their respective locations?
    2. There is a gray wire and I have no idea where this is supposed to go on the 7 blade connector. I think it is for keeping the refrigerator cool when travelling, but where would I hook it to on the 7 blade adapter?
    3. What wire do I hook to the PU battery positive post so that it gets charged while travelling?
    4. How do I switch from shore power to battery power so the interior lights and fridge work from the battery?
    5. This sort of ties to question #4 in that if the battery does not power the fridge is the propane supposed to and if so is there a manual which shows me how to get that system working? (Gas stove and fridge?) I have not tried anything thus far with the gas as I do not want to blow myself or the trailer up.
    6. The PU has a fresh water tank, but not a drain tank as far as I can tell. So in the sink, it has a drain, where does the drain go to or does it just run outside? No bathroom so its not that kind of water.

    I hope that someone can help us out here with these and thank you in advance. Hoping to take it camping for the 4th of July this coming weekend.
    Sincerely, Matt
  2. tombiasi

    tombiasi Well-Known Member

    Likes Received:
    Sep 1, 2012
    Northwestern New Jersey
    The battery negative should also go to trailer frame. You only need the 7 blade white if this is done.
    The gray may be 12V aux to keep the battery charged but its usually black. Trace it to see what pin it goes to.
    Your converter may switch to battery automatically, if you see a transfer switch that specifies AC or Batt then you need to do it.
    Most campgrounds would frown upon letting gray water on the ground. Use a bucket.
  3. Raycfe

    Raycfe Waterford Ct.

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    Oct 3, 2007
    Waterford, Ct

    Tie all your grounds together ..... Battery negative to frame ....trailer plug to frame ...... convertor housing to frame. the frame is one big ground wire.
    Black wire is trailer harness to battery positive and to feed the 12 volt power to the convertor.
    Because the harness only has 14 gauge wires in it would be a good guess that they ran a separate Gray power wire for the fridge.

    As for your convertor we will have to know more about its make and model ......... Some have a CONV/OFF/BATT switch to control which source to 12 power from. and usually this convertor will not charge the trailer battery. Others are automatic and may have a built in battery charger.

    Don't dump the gray water on the ground.

  4. rabird

    rabird Howdy!

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    Mar 3, 2006
    N. TX
    Matt D Bushnell, please do the helpful folks here a favor, add 98 Palomino Mustang and any other stuff to your signature so it shows on every post, thanks.

    A '98 should not have a conv/off/batt switch, once connected the battery will always be available, like if power goes out the battery will take over for the 12v stuff. Leave a light on unplug from utility power and your battery drains, propane/CO detectors (if installed) are always on which may mean disconnecting the battery in storage.
    Report your power center make/model and there may be a manual available.
    Last edited: Jun 30, 2020 at 8:28 AM
  5. McSkippy

    McSkippy Member

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    Sep 10, 2019
    The grey wire is probably back-up lights.
    myride likes this.

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