Trailer lights off completely - Where to start?

blake_a

Active Member
Trailer is 15 years old and lights have worked fine but are now completely off. Anyone know where I start and what equipment I need to diagnose the problem?
 
I would check the ground connection first. See if you have 12volts between the trailer and the ground wire at a light with the lights on. If you do, no connection.also run a wire from the tow vehicle to the trailer to see if the ground between the vehicle and trailer is made. Other than that, learn to use a meter and look if you have Voltage at the lights.
 
Make sure your ground wire is not broke off, I would bet it's that if they all failed at the same time.
 
I'd be very surprised if it's a ground. When your trailer is attached to your tow vehicle, the trailer/vehicle connection is basically a ground.
 
Try a different truck first to know if its your truck, or the trailer. Then move on from there.
 
Get yourself a 12 volt test light if you don't have one. Start with the electrical connection on the tow vehicle. Connect the ground clip on the test light to a GOOD ground on the tow vehicle. Turn on your hazard lights and the running lights. Now stick the probe of the test light in the electrical connection. You should see the light come on when you touch the metal part of the connection. The light will flash with the hazard lights and be lit with the running lights. If you don't get anything on this test you may not have power to the connector. If this is the case check to see a fuse isn't blown. Start there to make sure you have power to the connection. Once you confirm this you can move on to the trailer. There will be a ground wire for the trailer. Check to be sure this is okay.You Tube is your friend. I would imagine there is lots of info there.
 
Ok great. Thanks to everyone for the info. I will get a 12 volt test light and sort it out next weekend.
 
15 years old? Don't mess with it. Rip it all out and replace with new. Much easier and cheap. But you have like 20 other responses telling you to fix it.. How do you know which advice to take?
 
15 years old? Don't mess with it. Rip it all out and replace with new. Much easier and cheap. But you have like 20 other responses telling you to fix it.. How do you know which advice to take?

now that makes sense !
it may take an hour or so, but once you have a new hiring harness and lights
you'll be happy.
 
Yeah there are definitely some shoddy looking wires in there and I was already having trouble with the right tail light...... Maybe I should install the new one.... Thanks for the Amazon find, that looks like a good deal. I'll check the truck and check over all the connections and then if I am not getting anywhere I will order the new one. Thanks again for the help and advice.
 
now that makes sense !
it may take an hour or so, but once you have a new hiring harness and lights
you'll be happy.

You must be speedy gonzalez. It took me more than that just to remove the tail lights , marker lights, rear red lights and the old crappy wiring. Stuff was solidly corroded

Oops, you said hiring harness, never done one of those. :D

Good advice from Island Fish Lifter, chuck it and start fresh. Even if the trouble is with the truck this time, next time it will be your old lights.
 
When you are ready to remove all the old wiring, it is good idea if you use some string and attach it to the wires, so that when you pull it through the frame, you leave the string in the frame. You can then attach your new harness to the string and just pull it through.
 
Do the trailer lights have to be fastened to the trailer ?or may they be off compleatly on a light bar with light over plate?my light bar has lasted 10 years without fail ,it never gets wet.
 
When you are ready to remove all the old wiring, it is good idea if you use some string and attach it to the wires, so that when you pull it through the frame, you leave the string in the frame. You can then attach your new harness to the string and just pull it through.

This is a good thing to remember to do as well. Not fun trying to pull/push wiring through without a string leading the way. And use a heavy string because it can get hooked up and cut easily inside the trailer rails.
 
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