Trailer power plug

Discussion in 'On the Road' started by K8INA, Aug 9, 2016.

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  1. KF5FEI

    KF5FEI Ham Member QRZ Page

    Could be worse. I had to install a factory tow harness in my Dodge (Mercedes) Sprinter, and it required taking the dash apart, tapping into the brake light switch, some wiring under the driver seat and hood, and bundling up an extra 4 feet of wire that was unused on the shorter vans. One boo-boo they made was connecting the trailer brake wire straight up to the brake light switch. They left the wire disconnected on later versions, and later deleted it from the harness completely. I think I have only used it for small trailers, and the 12v line gets used for backup spotlights and to power the flashing stop lights on the crash bar in the back.
  2. KL7KN

    KL7KN Ham Member QRZ Page

  3. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Pin 4 is the 12volt its dedicated for 12 volt RV Trailer charging car are auxiliary batteries on any type of trailer
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    Being Black could cause some confusion. Reverse polarity. :eek:
  5. KD2IAT

    KD2IAT Ham Member QRZ Page

    That's the funny (odd) thing about travel trailers and fifth wheelers. For some unknown reason, that industry has settled on white being ground and black being hot. Unfortunately, that logic has extended to the tow vehicle side of the standard 7 pin trailer connectors as well.
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    AC and DC gets many people confused.

    People that work on autos think that Black is ground on a home AC power wire.

    They wire their AC outlets backwards. :eek:

    Standard confusion is a industry standard.
  7. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    White's always neutral for electrical codes in most cases, green is ground world around except in my ham Shack hi hi!!!!!!!!
    KA9JLM likes this.
  8. AG6QR

    AG6QR Premium Subscriber QRZ Page

    RVs and trailers generally use the house standard: White is neutral/chassis/ground, black is hot/positive. Cars use the convention of red being hot/positive and black being chassis ground. I used to own an RV that employed both conventions: any wiring installed by the RV conversion company used the RV/House standard, while wiring installed by the chassis manufacturer used the automotive standard. The deep cycle house battery had a black cable to positive and white cable to negative, while the engine starting battery had a red cable to positive and black cable to negative. The great thing about standards...
  9. KF5FEI

    KF5FEI Ham Member QRZ Page

    ...Unless it is a German vehicle, and then DC ground is brown. But at least they've stuck with the same wire colors and terminal numbers through the years.
  10. W9JEF

    W9JEF Platinum Subscriber Platinum Subscriber QRZ Page

    It's a long way from that truck battery to the trailer connector.
    While the wire may be able to handle 20 amps there's that pesky
    I×R voltage drop. At a mere .05 ohm wire + contact resistance,
    with 20 amps, you lose 1 volt. Some radios don't like their supply
    to fall below 12 volts.
  11. KF5FEI

    KF5FEI Ham Member QRZ Page

    I think I mentioned this a few pages ago. I suggested he see what size wire it was, and estimate the length.
  12. W4KJG

    W4KJG Subscriber QRZ Page

    Don't assume anything, especially when it comes to European AC wiring colors and some European DC wiring colors. Ground/earth for AC will almost always be green-yellow, but neutral could be blue or black, and hot single phase could be brown, black, or red depending on when it was wired.
  13. K8INA

    K8INA Ham Member QRZ Page

    Thanks for the help, everyone. I had already checked all of the manuals, but they did not list the trailer wiring. Guess because it's an option. The normal round 7 blade connector is wired for lights, brakes, and to charge the coach battery. I simply needed a quick answer to what current the charge circuit would handle. While the blade will handle 50 amps, I wasn't sure what the chassis wiring was, hence the question. I finally crawled underneath the truck, checked the wires, followed them to an add on fuse panel, and determined it was rated for 35 amps. The only caveat was the key has to be in the ignition or accessory position for voltage to be supplied, but that's not a real problem. So, again, thanks one and all.....
    Jeff K8INA
  14. AC0GV

    AC0GV Ham Member QRZ Page

    They are relay switched, On my Ford up-fitter switches I removed the relay and installed a jumper made with 2 spade lugs.
    Power to the switches at all times.
  15. KA9GDW

    KA9GDW Platinum Subscriber Platinum Subscriber QRZ Page

    My thought is to check your fuse panel for that connector.

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