Trailer lights not working properly (and brakes out too)

REDLYNER

REDLYNER

Mall Crawling Race Rig
Joined
Oct 31, 2008
Location
Mountain Island
Looking for a few suggestions to help diagnose what's up with my trailer.

It's fairly new (about 6 months old or so) and now the lights and brakes aren't working.

Brakes:
Hooked up to a Tekonsha brake controller- was working, now brake controller says no connection to trailer.



Lights:
With head lights on, no trailer lights work
With head lights off, brake lights dimly light up (running lights I believe)
Left blinker works, right blinker does not.


I don't see any torn wires, any suggestions on how to trouble shoot?
 
have you checked your truck fuses to see if they are all still good. I thought i had messed up my wiring bad and thats all it was. the left blinker working and the right doesn't make me think that it could be a fuse. Its any easy starting point to start at, also make sure all your grounds are good still.
 
You've got a broken wire or very poor ground somewhere. What brand trailer? Look above the axles for pinched wires, find out how the trailer grounds.
 
Is the trailer hooked up to your truck or are you just plugged in testing? You need to be grounded to the truck.
 
GotWood said:
Is the trailer hooked up to your truck or are you just plugged in testing? You need to be grounded to the truck.
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Hooked up to the truck.

braxton357 said:
You've got a broken wire or very poor ground somewhere. What brand trailer? Look above the axles for pinched wires, find out how the trailer grounds.
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Red Hot Welding built it for me. I'll have to go back and check the wires, what fuses would I check?
 
Your truck will likely have a "trailer" fuse and possibly relay. But being that the brake controller is working and you do get some lights, blown fuse is almost ruled out. If a non-trailer builder put it together then you're on your own :flipoff2: Even most trailer mfr's can't do a decent wiring job/use the cheapest shit possible. You have a loose or pinched wire somewhere on the trailer I'd put a dollar on it.
 
braxton357 said:
Your truck will likely have a "trailer" fuse and possibly relay. But being that the brake controller is working and you do get some lights, blown fuse is almost ruled out. If a non-trailer builder put it together then you're on your own :flipoff2: Even most trailer mfr's can't do a decent wiring job/use the cheapest shit possible. You have a loose or pinched wire somewhere on the trailer I'd put a dollar on it.
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I'll go through the wires this weekend. Red Hot Welding is a trailer manufacturer.... Unless you are just trash talking them over a Gator or something. :)
 
Make sure all the connections are clean (those 7-wire connectors always seem to "crud up). Use some silicone dielectric grease on the plug/pins. As mentioned above, it sounds like a bad ground for that. Loosen up the chassis ground, clean the connections, grease and hook back together.

On the blinkers I always find that those little bulbs corrode fairly quickly. Pull the covers off, clean and grease and reassemble. Also a lot of trailer manufacturers use 1-wire lights that use the trailer frame for ground. That's great and cheap but results in poor grounds to the light housings after some time with the elements. Again clean, grease, re-tighten.
 
Sounds like a bad ground. Make sure there is a ground wire in the 7-pin and that it is well connected at the trailer frame. Check the trailer wiring for scotch locks. Remove all that you find and replace them with properly soldered and heat shrinked splices.

As others have stated, it's working a little bit, so it's not a fuse.

If you get deep into rewiring it, consider buying a trailer junction box to install where the 7 pin pigtail meets the trailer frame. It's basically a weather tight box with seven terminal blocks inside. Makes for a handy place to check voltages, you can install fuses or LEDs insde for easy trouble shooting, and it makes replacing the pigtail a snap.
 
Loganwayne said:
not always true my truck had fuses for brakes, running lights, left, right, and reverse lights.
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Sure, but he drives a newer tundra and the new toyotas have 7 pin hookup from the factory with their own shit, he's not scotchloking onto the tail light and turn signal wires. While it's always a possibility, it is unlikely. And if it is a blown fuse, then there is still a trailer wiring issue that needs to be resolved. I will trust factory toyota wiring over any trailer mfr in America any day.
 
braxton357 said:
Sure, but he drives a newer tundra and the new toyotas have 7 pin hookup from the factory with their own shit, he's not scotchloking onto the tail light and turn signal wires. While it's always a possibility, it is unlikely. And if it is a blown fuse, then there is still a trailer wiring issue that needs to be resolved. I will trust factory toyota wiring over any trailer mfr in America any day.
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Your right if it's blowing fuses something is wrong. My 01 250 has a factory 7 pin and that's how it is wired with everything having it's own fuse. I just thought that checking the fuses could be a simple quick fix since I went threw a very similar thing about three weeks ago and could have saved my self some time checking the fuses first. If this is the first time he hooked up this trailer to this truck it could have nothing to do with his trailer, the person that owned the truck before him could have had a trailer that blew the fuses and with out checking he would never know that. ( that is what happened to me)
 
Went through somthing similar on a friends 2012 tundra. Its worth a shot.

On the truck the groud wire came off the back of the plug and went up to the frame rail. It was o ringed and bolted to the frame. The bolt had worked loose AND the frame was painted not cleaned at the connection point.

No idea if his was factory or not, but it looked like it.


A loose ground connection would almost assuredly cause the symptoms you describe. The ball to tongue should provide some path to ground as well but a newer truck, coated hitch and coatced insert could isolate that as well.
 
braxton357 said:
Sure, but he drives a newer tundra and the new toyotas have 7 pin hookup from the factory with their own shit, he's not scotchloking onto the tail light and turn signal wires. While it's always a possibility, it is unlikely. And if it is a blown fuse, then there is still a trailer wiring issue that needs to be resolved. I will trust factory toyota wiring over any trailer mfr in America any day.
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My dads Chevy has fuses for trailer running lights, trailer turn signals, trailer back up lights, etc. under the hood. All separate fuses from the truck lights. I think that is what loganwayne was referring to. And I agree with everyone else, it sounds like a ground issue.

Duane
 
I just checked the fuses under the hood, everything looked good. Sidenote- I just hooked up my boat trailer and have the exact same problems. I guess that rules out the trailer and the fuses.


Ron- I'll check the trailer hitch ground in the morning.
 
Electrical problems are the worst!

I would suspect a bad ground somewhere. I didn't read all the responses but my guess would be the ground at the truck side connector.

Just rewired my boat trailer, I know how ya feel!
 
REDLYNER said:
Sidenote- I just hooked up my boat trailer and have the exact same problems. I guess that rules out the trailer and the fuses.
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It's a Toyota. Frame probably rusted in half, and there's not a good ground connection from the rear bumper to the battery anymore. Might have to run a ground wire. :flipoff2:
 
Update:


I couldn't find where the ground attaches to the frame or bumper, it's in a wiring harness/loom that goes deep under the truck. But I did look at the 7 pin connector in the light and noticed some corrosion on the pins. So I hit it with battery post cleaner and tried to file it the best I could (tight quarters). I hooked up the boat trailer and all lights seem to be working like they should.

I'll hook up the jeep trailer this weekend for another test.

Thanks for the help!
 
Update update....


Towed the car hauler out to the Flats and nothing changed:

Brake controller still says no connection
Passenger trailer brake light constantly runs when truck lights are on
When truck lights are off- blinkers work on trailer. But trailer brakes do not.




Hmmmmmm
 
I'm sure you check your plug on vehicle with light tester? I start there...I had problems almost like this but found fuse blown in truck for trailer(I think my dodge has 2 or 3 fuses for trailer)

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No blown fuses in my truck.

I'm towing two different trailers, one now works like it should, but my new car hauler is not. The car hauler was working perfect, then the lights starting having issues, now the lights and brakes are having issues.
 
Are you 100% sure that everything worked correctly, but now it doesn't?

What about the other trailer? Is it identical? Has brakes, they work, lights all work, etc?

The reason I ask is that I borrowed somebody else's trailer one time, and it was wired incorrectly. Every time I plugged it into my truck, it blew the brake fuse, none of the lights worked correctly, some lit all the time, some never lit, others lit at inappropriate times, etc. The cause was that the labels inside the trailer connector (molded in place by the connector manufacturer) were completely incorrect and didn't match the way that any of the OEMs wire their plugs.

Have you checked the trailer with a meter? A 12v source and a couple of jumper leads would sort the trailer out in short order.
 
Have you hooked it to another truck? That might get you started in the right direction.

I would go through and rework every ground on the trailer. Most trailers have grounds right next to the lights. It only takes one to make things screwy.
 
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