Trailer lights not working

[jwanck11]

So I hooked up the electrical harness from the trailer to my new truck. turned on the lights in the truck and nada.

Not a single light on the trailer lit. I cleaned all the contacts to where there is shiny metal and the same thing.

Does anyone know:

1) Whether there might be a fuse between where the wires are spliced into the trucks brake lights and the harness (couldn't find one).

2) If one light is out, does that mean all lights on the trailer would be out?

3) Could a bad ground/short somewhere in the wiring in the trailer be taking out all the lights?

Where would you start to look?

I plan on running bare wires from the truck harness to one of the lights to see if it will shine. Any other suggestions?

[ImaPigDog]

One other thing to check is the fuse(s) on the truck. I had that happen to me once. If you have another 12V battery, you can wire it to the trailer lights to see if they work.

[Oklahoma Breakdown]

I have 2 separate fuses on my truck 02 GMC and both of them have been a cause for lights out in the past. Have you confirmed though that the trailer lights do indeed work off of another truck or that another trailer works on your truck?

[kerlee]

turn on your lights and take a cheap 12v test light and test the receptacle on the truck. you may not be getting power to the receptacle. I bought a used truck once and the cable was unplugged under the truck bumper...

[jwanck11]

Thanks everyone for the input.

I really would rather not splice into the wires if I don't have to and unfortunately I don't know anyone that has a truck to test that way.

All of the connections on the truck appear to be good. The tail-lights and license plate lights all work and the wire-taps (factory) are directly from the same feeds.

I will check the fuses as I haven't done that yet. A 12V tester is after that.

[zad0030]

Get your book out to locate the fuses as sometimes they hide some special ones.

[Iwndr]

If it is a Ford sometimes you have to buy a module for the fuse block under the hood unless it came with the towing package

[Fuh Sho]

are you lights grounded to the trailer or do you have a grounding wire run through the harness? My old trailer would do that same thing to me untill the hitch and the ball made a good contact then they would light up

[Dave S]

Get a test light from your local auto parts store and check the plug on the truck. If no light on test light, then truck is the problem. If you need more detail on using test light let us know and we can direct you more. Start with that 1st, process of elemination, truck or trailer? As said above, bad ground can make it not work or do goofy things also.

What kind of truck is it? I have a ford with towing package and a relay underhood was missing which caused reverse lockout switch to not work. had to add that relay myself.

[laserfish]

Had this happen on a Ford. Had a place for a fuse for the trailer wiring but had no fuse in the slot. Drove us nuts for a couple of days till we found it. Look in your manual.

[jwanck11]

Get a test light from your local auto parts store and check the plug on the truck. If no light on test light, then truck is the problem. If you need more detail on using test light let us know and we can direct you more. Start with that 1st, process of elemination, truck or trailer? As said above, bad ground can make it not work or do goofy things also.

What kind of truck is it? I have a ford with towing package and a relay underhood was missing which caused reverse lockout switch to not work. had to add that relay myself.

Yup, I have a Ford 2006 F-150 with the tow package. Checked all the fuses in the cabin and they were OK. I have to check the relays under the hood.

Judging from the harness on teh truck (one pin was corroded that I cleaned) I'd say the truck was used to tow in its past.

One odd thing is that the ground wire was cut and not connected to the trailer, but the lights worked last year. I stripped the cut wire and touched it to the trailer and hitch and it made no difference so I do not think this is the issue.

Off to the auto store to buy a 12V tester.

[Barefoot]

If it has a swing tongue on the trailer, make sure the pins or the hole the pins go in aren't rusted. I chased my lights not working for 3 hours before I figured out that I needed to run a new ground past the swing tongue.

[jwanck11]

I dont have a swing tongue... and the ground wire was never connected. It was cut between the harness connection on the truck and the trailer. The lights were working so I do not think it is the ground - as far as I am aware, the ground is not being used as a neutral, but as a proper ground.

WEll, the ghost is somewhere in the trailer. Just got back from the Dealership and they were nice enough to hook up a tester onto the truck harness and all electric was A.O.K.

Now I have to get a 12V test light to test the trailer wiring until I find the point(s) of failure.

At some point I will decide to run new wiring!

One thing I found is that my trailer is rusting from the inside out and there is nothing that I can do about it. Damn salt water!

This is the route that I might just go and say the heck with it!

[laserfish]

If you are seeing corrosion, be sure the ball and tongue are not corroded. This will keep the ground from going from the truck to the trailer. Most do not hook up the little white wire, the ground runs from the stinger/ball to the trailer tongue, all places where corrosion can prevent good conductivity.

[jwanck11]

Thanks LF. The ball and tongue are OK. I even bypassed that system by stripping the white wire and touching it to the trailer and then the coupler and nada.