Please help me troubleshoot this electrical problem on my utility trailer.

Same problem exists when hooked up to both of my pickups, 98 & 99.

Both blinkers worked.
Both stoplight worked.
Running lights did not work.
Night-time trailer lights did not work.

I found some corrosion so I put all new wiring, lights, and ground on to a different part of the trailer, and the same problem persists.

When I turn on my headlights, the trailer lights do not come on, but...

Both blinkers work.
Both stoplights work.

I figured I'd wait to wire the running lights back in, until after I get the night-time lights working.

Could this still be a ground problem, and if so why do the stop, and blinkers work? Thanks.

 

wire your running lights and you will have all your lights.

there are no night time lights they are your running lights.

Four wires brake/lt turn, brake/rt turn, running lights and ground.

 

Brake lights and turn signals as far as your trailer is concerned are the same. There are two circuits - dim light (taillights) and bright light (brake and/or turn signal lights). If you have no ground the brake/turn signals may appear to work by grounding through the bright filament and lighting the dim filament. This is 99% of the cause if you see someone whose brake lights work until they turn on the running lights. At that point the running lights work but when they hit the brakes the lights go out instead of getting brighter.

DPorter has the right idea. Wire everything and see what you have, diagnose from fully connected not from a partial wiring job.

 

Thanks for the responses...I will wire up the running lights, and give it a try.

 

Let us know what happens please.

 

do you have a test light?

 

I wired up the running lights, and still no joy.

Cleaned all points where the new lighting system attaches, and in the receptical, still the same.

Changed out the receptical adapter, no help.

Moved the ground to a different part of the trailer, cleaned down to bare metal, no help.

The blinkers and stop lights work fine, just no running lights, makes no difference hitched up to both of my trucks.

I'm still believing it is a ground problem, but can't find my tester.

 

There should be a relay in the underhood fuse block for running lights.

 

Take a single jumper cable, hook it to the trailer frame (grounding point for all trailer wiring with possible exception of electric brakes, depending on how they were wired) and hook the other end to the frame of your truck. If there is a ground problem between the truck and trailer this will "fix" it and you can go that route.

 

I had this problem with my car hauler when I re wired it. It turned out that when I put my marker lights on the wire on 2 of them were off centered in the hole they ran through and when I tightened the light down ithe edge of the hole cut into the insulation causing the lights to be grounded out it sook three days of troubleshooting to find it. just one more thing to check.
If you're not quite sure on what wire goes where here is the color code.
White= ground
yellow= left turn and brake. ( in RV application left turn is red.)
Green= Right turn and brake. ( in RV application Right turn is brown.)
Brown= Running lights. ( RV application running light is Green.)
Blue= Electric Brakes
Black= Auxillary (constant Power)

 

To make sure your ground is okay...run a wire from trailer frame to the neg (-) side of the trailer battery!

 

I went to Walmart and bought a new 7 to 4 prong adapter w/led.
The running lights were not showing any juice on either vehicle. I checked the 20A mini-fuses, in the power dist. box, and sure enough they were blown on both trucks.

Put in new fuses and I get power to the led, but as soon as I hook up the trailer and turn on the lights the fuses blow.

So now I assume the problem is in the trailer wiring. Which is all brand new and wired according to the diagram.

 

OK, is there a chance your running lights are connected to ground? This would blow the fuse as soon as power went to the running lights. like, not on the negative side, but on the hot side. If you spliced 2 running lights together and accidentally grounded one hot, that's all it will take.

Start disconnecting fixtures one by one until it doesn't blow the fuse and then you'll know where the problem is.

-Jer

 

That's a LOT of fuses,,,,I'd wire in a resettable breaker type fuse.

 

Ok, I meticulously checked each element, and on the yellow side, discovered a smashed wire that was apparently grounding out to the brown running light wire.

The plastic insulation along all of the new wiring seems to be brittle, of inferior quality, and prone to break and crack.

So I bought a new harness and carefully rewired it. It all works fine now.

Thanks for the help!