Trailer Lights?

[Lucrestyle]

Ok here's my problem, my lights don't work, no signal or break lights, but all running lights work .. (ie when i turn the lights truck light on the all glow, but still no break or siginal) anyone have any advice to fixing this problem or diagrams thanks alot

 

[BrianS.]

Re: Trailer Lights?

Check your fuse box on your truck.

 

[CATransplant]

Re: Trailer Lights?

First off, do the turn signals and brake light work on the tow vehicle when the trailer plug is not connected? If so, then the fuse and flasher are OK. If not, start there.

Next, make sure the contacts on both connectors are clean and not corroded. Then test again.

If you still have no lights, start with a multimeter or a test lamp, and check for voltage at each pin when you have the turn signals on. You should see voltage on the pin that handles the turn signal for the side that's working. If not, then you'll need to check your wiring harness and connections on the tow vehicle.

If all is OK in that test, get your battery charger out, and a couple of finishing nails. Connect the negative side to the plug's ground connection, then probe the contacts on the trailer side, checking for lights on the trailer.

If still no lights, then you'll have to examing the wiring, bulbs, sockets, etc. Check the bulbs and sockets for corrosion.

A common problem is a poor ground, but since you have running lights, that's probably not the issue.

Eventually, you'll track down the problem.

 

[jtexas]

Re: Trailer Lights?

Is this a recent development, or did you only just install the trailer harness on the vehicle, and if so, is it a late-model vehicle with separate lamps for turn and brake, and if so, did you get the right adapter?

Truck lights work doesn't necessarily rule out blown fuse - many vehicles have separate fuses for trailer lights - example, my Explorer has a fuse for the left trailer brake/turn and one for the right trailer brake/turn, but no separate fuse for trailer running lights. Check the fuse diagram in your owners manual.

couple bucks at Walmart, I bought a little trailer harness tester, plugs into the vehicle trailer harness, with LEDs that light up when you turn on lights, turn signals brakes - handy little gadget, quicker than pulling fuses.

"A common problem is a poor ground, but since you have running lights, that's probably not the issue." - I generally agree with that statement, but note that the brakes/turn signals use more current than taillights therefore are more vulnerable to a weak ground - ground connection can be good enough for taillights but not for brake/turn - so I'd check the ground connections before doing anything else.

If you've got a 4-flat connector, the taillights are the brown wire, green is right brake/turn and yellow is left brake/turn.

 

[bruceb58]

Re: Trailer Lights?

To check if the running lights are getting a "sneak path" ground through the turn signal bulbs, pull the bulbs out of the turn signal lights and see if you side clearance lights stay illuminated.

 

[Lucrestyle]

Re: Trailer Lights?

I will take a look at the lights this afternoon and see if its a ground or a corroded wire. thanks for the advice boys, its great!

 

[Esox]

Re: Trailer Lights?

I had the same problem a couple months ago. The running lights were working but the brake/turn lights didn't. There was a short in the trailer wiring that was blowing the "trailer tow" fuse in my tow vehicle. I ended up just rewiring the trailer.​