OEM trailer wiring mystery

[dabear]

I spent the weekend under the GW rebuilding the OEM trailer wiring box electrics....new relays and fuse (both were a bear to find BTW). Well I hooked up the 7 pin to 4 converter to the trailer and my running lights work along the side of the trailer and right rear (not left) and neither brake or turn lights work. I hooked up my Bronco and the trailer lights are in good order just to check.

I didn't change any wiring simply unpluged the relays/fuse and reinstalled...any idea why only a portion of the lights work?

[crispyboy]

I would check the pinouts coming out of the Jeep to make sure they are working properly.
The second thing that typically goes wrong is the ground. A good ground is extremely important or your lights will do screwy things. Make sure the ground is good on the trailer, through the connector and good on the Jeep. I use dielectric grease on all the connections to make sure they do not rust in the future.
I did the same thing you did and rebuilt the stock box on the frame.

[chrisnsarah]

If the Bronco lights it up ok, then something is amiss with the Jeep. Doublecheck all your connections again, make sure they are connected to the correct pins. There is a wiring standard for these trailer connections and all the adapters sold use this pattern.

Put a tester on the pins and see if they function correctly.

If you were going off a wiring diagram or picture, be sure you weren't connecting in a mirror image, ie. looking at the back when it's supposed to be the front side. Check the grounds too. I always run a separate ground from the vehicle to the trailer, since I've had bad luck with rusty trailer balls.

[Jayrodoh]

Sounds like something is amiss in the box. The brake/turn are combined so it runs through two relays triggered by the factory lights. IF the factory lights work, pull the box apart again and make sure the relays are clicking in sync with the lights, one relay for left and one for right. If not, then they are not getting power from the harness. IF they are clicking in sync, make sure that the relays are feed power from the circuit breaker.

If you need help, I've rebuilt a few of these boxes and can do yours if needed.

[dabear]

Thanks for the replies...

...I'll take a picture over the weekend and post to see if I have the right layout inside the box. I am getting power to the box but haven't tested the outgoing lines yet. Inside the box w/ the 4 relays was a 10A breaker...I saw a post that this was supposed to be a 30A. Which is correct? Thanks again.

[chrisnsarah]

4 relays? Mine only had 3. Left/stop, right/stop, and running lights. There was a breaker but I don't recall the amperage. The relay power lead is supposed to piggyback off the electric tailgate circuit.

[Walt]

Are you POSITIVE that the relays are the right ones?
I had similar issues when I didn't look VERY closely at the little wiring diagram on the new relays.

[dabear]

Well, I replaced what was in the box.

As best I could tell the box had never been opened and it was all original. 4 87A 5 way relays and one 10A breaker.

There is one ground wire inside the box, does this ground to the box itself?

[Jayrodoh]

10amp breaker is fine. If it blows, you'll have no lights on the trailer. The tailgate circuit is 30 amps.

The box is grounded through the mouting tabs to the frame, but if your running lights work, ground is not the issue.

Make sure pin 30 on the socket has power at all times for each relay. Pin 85 should be grounded at all times as well for each relay. If that is good, now check the other pin 86 for power (one for running lights, one for right brake/turn, one for left brake/turn, etc.) when the appropriate light is on. IF that is good, check continuity from the 7 way round connector to pin 87 on the relays.

Keep in mind there is one relay for the brake lights and then two that break that signal for the turn signals.

See http://oljeep.com/gw/elec/86/86_FSJ_...ramPage4-8.gif

[dabear]

Thanks Jayrodoh...gound ?

The wiring diagram really helps. My suspicion as you pointed out is the ground. Off of the 1st relay (C460) there is a short ground wire...does that need to be run outside the box to the frame to ground? I currently have it grounded inside the box w/ is attached to the frame.....sounds like that is my issue and I need to ground to the frame. I'm mechanically and not electrically inclined though....

To address an earlier poster's question, the diagram has 4 relays and one 10 amp circuit breaker in the box.

[Jayrodoh]

As long as it's grounded to the cover of the box you should be OK, the cover is metal and grounds to the frame when attached. If any of the lights work on the trailer, then your grounds should be OK. It's important to make sure that each relay is grounded though by checking for continuty.

Did you take the round trailer connector apart and make sure the wires aren't corroded where they attached to the connector? It's just screw terminals and the wire can be cut back and reattached if needed.