Trailer wiring question - I'm stumped...

[4play]

Most newer trucks have seperate fuses for the trailer circuits, and sometimes they are in their own fuse holder, it might help for you to let us know what truck you are working on. Also does the truck have seperate bulbs for the turn signals vs stop lamps. If so , it might not have been wired up right or the bulb integrator has failed.

If the actual ground wire (white) has not been hooked up on trailer and truck, then the trailer would have to rely on grounding through the trailer ball, I see this a lot and it usually causes intermittant lamp operation and flickering lights.

 

[Harley1953]

Most newer trucks have seperate fuses for the trailer circuits, and sometimes they are in their own fuse holder, it might help for you to let us know what truck you are working on. Also does the truck have seperate bulbs for the turn signals vs stop lamps. If so , it might not have been wired up right or the bulb integrator has failed.

If the actual ground wire (white) has not been hooked up on trailer and truck, then the trailer would have to rely on grounding through the trailer ball, I see this a lot and it usually causes intermittant lamp operation and flickering lights.

+1 on the above. I have a 2007 F150 and had this problem.. Pulled what little was left of my hair out.....I was sure it was a problem with wiring in the trailer. Truck still under warranty at the time.... Took it in and sure enough there was a little bitty fuse in the truck open that caused the issue... Service manager told me it was pretty common.....

 

[uniquediversity]

I had the same issue and the bulbs in the light kit wasn't a dual filament bulb and so check that. Brakes run off one filament and signals off the other. I think.

 

[zseese]

+1 on the above. I have a 2007 F150 and had this problem.. Pulled what little was left of my hair out.....I was sure it was a problem with wiring in the trailer. Truck still under warranty at the time.... Took it in and sure enough there was a little bitty fuse in the truck open that caused the issue... Service manager told me it was pretty common.....

Me too, on my 2010, the new "submersible" lights I had bought from atwoods were not actually submersible (had a large opening on the bottom), and when the hot bulbs hit the lukewarm lake water (don't think the lake was actually ever cool this year) they broke and blew a fuse that from reading the owners manual I wouldn't have guessed would affect the trailer lights and not the trucks, until I expended all other options and went through every fuse in the truck one at a time...

 

[NikatKimber]

I had the same issue and the bulbs in the light kit wasn't a dual filament bulb and so check that. Brakes run off one filament and signals off the other. I think.

Usually the dual filament bulbs are for Brakes/Signals and Running Lights. Brakes and signals are nearly always the same filament.

OP, with the 4 wire trailers, if you get either Brakes or Signals on both sides, then the trailer is not at fault; since as the diagram shows, they are run on the same wire.

 

[Phat Mike]

could also be the flasher relay not big enough for multiple lamps.

 

[dieseltech09]

use a test light and check the truck side of the plug. If thats good double check your grounds. An easy way to check the ground is to take a set of jumper cables, hook one negative to the exhaust pipe and the other to the trailer. If the lights start working you have a ground problem. 99% of the trailer light problems I see at work are simple ground issues. Most people dont ever hook up the ground wire when wiring a trailer

 

[T34r1tUp]

What year and model truck?

i have access to service information. i can post diagrams and fuse locations if that would help.

 

[dennishoddy]

Go to tractor supply, and get the test unit that plugs between vehicle and trailer. Its has led's to identify if the truck is the problem.

 

[dx3]

Guys - you are all right. Turns out there is a little fuse box under the seat just for trailers. Unfortunately I just found this out before I signed on here, only to find out everyone had already answered my question! Guess I should have checked back here earlier!! So thank you VERY MUCH!

No problem.
BTW! i think I am about to inherit the car, which I am actually looking forward to! Lol!
Wife is wanting a new one!
I think i saw you in BA a couple weeks ago between 61st and 71st on Elm.
Nice advertisement by the way!

Lucky man! I loved that car! And yes, that was me... Hopefully it gets me some business

Thanks again,
Jonny