@#&$% trailer lights

Nuzzy · Jun 10, 2007

Everytime I've tested my brand new trailer's lights has been during the day and all the brake and blinker lights have worked. So fast forward to tonight when I was leaving my Dad's and he asks me if my lights work :wtf: Sure enough, when my running and headlights are on, NO trailer lights! If I hit the brakes/flashers/turn signals, everything lights up just fine, just no running lights

Of course I make sure the plug's all the way in but still nothing. By the time I got back into Issaquah to park the trailer, weif lets me know that now, one of the brake lights stopped working too

Any brilliant ideas? It's a standard 7 flat pin connector and I used to power the running lights on Bunk's trailer just fine (except for the one that never worked). Spose I'll be checking grounds and testing wires tomorrow. Does anyone know maybe where I should start looking or has had a similar prob?

84Toyota4x4 · Jun 10, 2007

I had intermittent lights on mine once, then all of a sudden nothing, then it started blowing fuses. Turns out I was stupid and used a chain and chain break that pinched wires when I hooked the chain under the lip of the trailer. Found it, spliced them back together, and all was fine.

Just an idea, although probably not your problem.

~T.J.

Lucky Jeff · Jun 10, 2007

most of the time, when I hook up a trailer. My lights won't work (running lights). I have to tap the fuse box under the hood and they all of a sudden come on. I have a feeling it's a bad ground on the truck.

JOOP · Jun 10, 2007

check to see if the the connections are clean.

caddyman99 · Jun 10, 2007

Dude if it's a brand new trailer...........I would take it back to them and make them find the problem. As long as it's a trailer wireing problem they should take care of it for you.
Was the plug on the truck factory installed???

Bunk1 · Jun 10, 2007

fwiw my trailer has a funky rear light. I wanna tottaly redeck it and rewire it, But i think i'll leave that to the next owner:flipoff:

Lucky Jeff · Jun 10, 2007

caddyman99 said:
Dude if it's a brand new trailer...........I would take it back to them and make them find the problem. As long as it's a trailer wireing problem they should take care of it for you.
Was the plug on the truck factory installed???

doesn't have to be the trailers problem.

TreeClimber · Jun 10, 2007

Nuzzy said:
a standard 7 flat pin connector

I'd take this opportunity to re-wire to the 7 round. All of the big three use the 7 round as the factory plug which means most trailers will also come this way. And for what it's worth, campers, 5th wheels and trailers often use the same plugs but with a completely different color scheme for which wire goes where! I found that wiring my Ford to match common borrowed trailers is a big advantage. Anyone who borrows my trailer hasn't got to re-wire their truck, and if I ever borrow someone elses, it works easy.

Regarding your issues, I've also found most trailers are wired with butt-connects, and often that's the problem. Slide under and bet you'll find they're pulled loose.

Also double check the grounds on the trailer to the truck.

And finally, use a test light on the socket of the truck to make sure you're getting a tailmarker feed to the trailer to begin with.

Nuzzy · Jun 10, 2007

I've heard that occasionally, different makes of trucks put wires in different locations on the connector... Any truth to that?

I don't know if the harness is stock Dodge or not.

Nuzzy · Jun 10, 2007

TreeClimber said:
And for what it's worth, campers, 5th wheels and trailers often use the same plugs but with a completely different color scheme for which wire goes where!

The PO of my truck only towed a live in gooseneck horse trailer. Maybe therein lies the prob...?

Lucky Jeff · Jun 10, 2007

well if it's a flat 7, then no that's not stock. If that's what you're askin atleast

Nuzzy · Jun 10, 2007

Well, I got a wiring diagram for the flat 7 pin and went to work with the tester... Coming off the truck, I could get the elec brakes, L turn, and R turn to work, but the pin in the tail lights position wasn't powered. I also tested the 6 round pin in my bed where the gooseneck would hook up and also couldn't find a tail lights hot wire but could find the L/R turn. I got into the fuse box in cab and under hood but nothing seemed blown. At that point I ran out of time cause I have to jet to a friends for dinner

Haven't tried hooking up the trailer again to see if jiggling wires did anything...

I tried to trace what I understand to be the brown wire but it kept going into bigger and bigger bundles which in turn started to make my head hurt. Is there another obvious place to check where the offending wire might be fubared?

*edit* All the work the old PO had done to this truck was done at the Power Shop so I'm guessing that's who installed all the trailer hook ups as well...

Not Jobless · Jun 10, 2007

So with the flat 7 and the other 6 pin you couldn't find the running lights?

Just tap into the running rights going to the rear.

Didn't they check all that stuff when you picked up/bought the trailer?

caddyman99 · Jun 10, 2007

Lucky Jeff said:
doesn't have to be the trailers problem.

I know.....I also asked if wiring was factory installed.

Lucky Jeff · Jun 10, 2007

I'm amazed that a dually dodge didn't come with a factory round 7? Hell I've never seen that before.

Hey Nuzzy, try tappin on the pd (fuse) box a few times under the hood while the trailer is hooked up and lights on...

Nuzzy · Jun 11, 2007

Jobless said:
So with the flat 7 and the other 6 pin you couldn't find the running lights?

The running light corresponding pin wouldn't light up the tester on either the 7 or the 6. Didn't test the "brown" wire yet that supposedly is the running light wire but if neither connector is working, I have doubts the wire would be hot.

Just tap into the running rights going to the rear.

Didn't they check all that stuff when you picked up/bought the
trailer?

I could have sworn everything was working fine the first time I towed it home. The next few times towing it after that was in the light so my running lights weren't on.

Nuzzy · Jun 11, 2007

Lucky Jeff said:
I'm amazed that a dually dodge didn't come with a factory round 7? Hell I've never seen that before.

Hey Nuzzy, try tappin on the pd (fuse) box a few times under the hood while the trailer is hooked up and lights on...

Just to make sure that I'm using the right terminology, this is the kind of connector I'm talking about. Not this exact one, but the style of the flat pins is the same.

Lucky Jeff · Jun 11, 2007

ohhhhhh, hah, I gotcha. Yea that's factory. No wonder i had never heard of a flat seven.

And it isn't all the time that I have to tap the fuse box. Damn truck seems to have a mind of it's own of when it wants to and doesn't want to work.

TreeClimber · Jun 11, 2007

That's generally referred to a 7 round.

nick c · Jun 11, 2007

Not sure how they wired up your connector but I found on a friends truck that had a trailer light harness installed they used a t-connector that went in the tail light wirring. Pretty common from what I've seen, but he had issues with his trailer lights working intermitnetly. After checking everything else i found that the t-plug was loose and barely touching so the lights would work once in awhile but once you got moving they would usually just flicker occasionally. shoved in together, used a zip tie to secure it and all was good....

the plug I'm talking about is usually up under the bed near the middle of the bumper. might be worth looking for.