4-pin to 7-pin trailer wiring adapter Problem

Discussion in 'First Time & New Camper Owners' started by jaxbuckeye, Nov 30, 2012.

  1. jaxbuckeye

    jaxbuckeye New Member

    Nov 30, 2012
    My new (to me) Viking PUP trailer has a 7-pin "round" electrical connection including electric brakes. Here's the adapter I have: http://www.etrailer.com/Wiring/Tow-Ready/30717.html When the 4-pin side of the adapter is plugged to my 4-pin harness on my vehicle, the 7-pin side of the adapter works. The trailer lights work as well, however when I plug the 7-pin trailer harness into the 7-pin adapter the trailer lights don't work. I hold the ground wire to my hitch. Has anyone had a similar issue?
  2. tombiasi

    tombiasi Well-Known Member

    I'm not quite sure what your problem is. You connect your 4 pin to your vehicle and then connect the trailer to the adaptor and everything works.
    What else do you need?

  3. CamL48

    CamL48 New Member

    Feb 20, 2012
    The 4-pin on your vehicle will only supply the power/signals that control lights: running lights, turn signals, brake lights, and back-up lights. A 7-pin has additional lines that carry electric brake signals, power to charge batteries, and another aux line for some other trailer options and features (anti-reverse, e.g.).

    The pig-tail adapter you linked to has provisions to run manual lines to connect for the additional 3 lines that your vehicle's 4-pin connector doesn't have. E.g., there's a line that you can run directly to your brake controller so that you can use your trailer's electric brakes. Or, you can ignore those 3 additional line outs and simply use the 4-pin signals that control your trailer's lights.

    This is the operative photo of your adapter:


    Now, if what you're saying is that your vehicle's signals are being properly routed through the adapter but that same signal is not making it through your trailer's electrical system to its lights, then you have some sort of electrical short in your trailer's wiring (and has nothing to do with 4-pin/7-pin adapters).

    Ideally, you could plug the trailer into another vehicle with a 7-pin factory harness. This would be the best way ensure that it's the trailer at fault. Alternatively, you could use a circuit tester (or even a simple voltmeter) to ensure that the pin-outs on the adapter are generating the proper signals.

    Assuming that the vehicle is fine and the adapter is fine, you'll have some work to do chasing down what is most likely a grounding issue. I hate, maybe more than anything else, trying to find the source of an electrical wiring problem.

    Good luck.
  4. tombiasi

    tombiasi Well-Known Member

    He needs to properly ground the TV side and make sure that ground is wired to the trailer.(Please don't rely on a ball hitch ground [:O]
  5. ChocoChock01

    ChocoChock01 On the road aagaain See Rallies below;

    Mar 7, 2012
    I love how they standardized on WHT Grd!
  6. BroRobin

    BroRobin New Member

    Nov 6, 2012
    When we bought our used NTU 1995 Starcraft, the camper's light harness had a four pin connector like a boat/utility trailer harness. The PO had a 4 Pin to 7 Pin adapter that she gave me. I plugged it into my 2004 Dodge Ram(I've only owned the truck since March '12) factory installed 7 pin receiver and none of the lights worked. I then looked under the bumper and saw there was a standard 4 pin connector wired in (aftermarket I'm sure) so I plugged it in there and the lights worked. :) I've not had the time to trace down the issue yet. [RTM]
    I'm not sure but I don't think the PUP has brakes, but I think I would like to correctly wire the harness to a 7 pin connector even with no brakes/controller needed, I would like to have a 12 volt source in the connector to power the existing porch light by the door and the street side porch light that I bought from eTrailer and will install soon. That way I can have lights while still "hooked up" to my TV for after dark setup. But I will need to make sure my TV 7 pin connector is functioning properly. (I hate to have to lay on my back and look up to work on the wiring on the TV, actually an inner ear problem is not conducive for working like this, I actually get dizzy and swimmy headed). [:(O]
  7. poohsta3

    poohsta3 Poopup

    Mar 15, 2013
    I have the same adapter just picked it up so that I can take the popup home with lights-DO i still need to attach that ground even if I dont need the brakes etc ?????
  8. tombiasi

    tombiasi Well-Known Member

    Doesn't that adaptor specify to ground the white wire?
  9. PNW Family

    PNW Family New Member

    Dec 3, 2012
    Yes, you MUST ground the large white wire, because on those adapters, the small white wire coming from the adapter side of the 4-flat connector are not grounded or connected to anything. If you do *not* ground that large white wire, you will have an open ground, and the circuit will not be completed. Nothing will work.
  10. poohsta3

    poohsta3 Poopup

    Mar 15, 2013
    ahhh I see!~ I had assumed that white wire on the 4 side of the adapter was the ground. Ok makes sense now! thanks! ( sooo glad I found this site ) [8D]
  11. goblinn2

    goblinn2 Midlothian, VA

    Jun 26, 2011
    when you are attaching the hot(black) wire up, disconnect your battery. Nothing nay happen, but better safe than real electrical problems.

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