Okay, I have a weird one here and am hoping someone else has seen this and has some ideas. I have a 2004 CCSB, D/A Chevy, and I have no right brake light signal on the trailer plug. I have right turn signal, which would indicate the fuse is fine (unless there is another fuse besides the rt turn/stop fuse that I don't know about). I have a left brake light signal. I have both brake lights on the truck. Any ideas?

Factory wiring on the truck?

That's what I'm thinking. I chased the wiring a little the other night, and it appears that the truck wiring and trailer wiring combine somewhere in the main fuse box under the hood, but have not started tearing into it yet. The factory service manual doesn't really address it as far as I can tell, so it may be time to suck it up and go see the dealer.

Sorry, I should have make myself more clear. I was asking if it was factory wiring or if someone added it in after.

I would go to the dealer. There is a module somewhere that combines the turn signal brake lights. I'm not sure how it is done as I have never looked into it but I suspect this might be the problem.

I would start in the junction box on the trailer.Test light can check the recepticle at the back of the truck to the trailer. Green with no tracer should be Right brake light.Green with Black tracer should be right stop light.Brown with no tracer should be for running light.

If he has the signal and no brake light on the one side it can't be the trailer.

Yes, it is factory wiring. I am leaning towards whatever module combines the brake and turn signals, so off to the dealer I go!

Check the fuse box, inside, left side of the steering post. Mine had a fuse out.

Used to be that the brake and turn signals were managed through the turn signal switch. If you still have the warranty I would let the dealer sort it out. Hopefully something simple like a fuse but I can't see each side having its own fuse.

To give everyone an udpdate, after two trips to the dealer I finally have some resolution, the turn signal switch module was apparanlty faulty. Of course once it hit the shop it became intermittent, but I finally convinced them to try a little harder and look deeper.

I have a similar problem, experienced on two different trailers.

I have my factory wiring. Both trailers have 4 pin flat connectors. I have used both the oem 7 to 4 and an autozone 7 to 4 adapter. In both cases, on both trailers, turn signals and brake lights work fine. Running lights do not work (i.e., clearance lamps and "headlights on" lights do not work).

Any ideas? Truck is under warranty so don't mind taking to dealer, but I like to give them a heads-up on where to look...

I just tried to sort out the same problem on a friend's truck. Same scenario; L & R turnsignal, but no taillights. There is no power to that pin in the 7 way socket on the truck. It's still under warranty, so I sent him to the dealer. Let me know if you figure it out. Thanks.

I had the same problem, it was the fuse under the dash by the steering column. It was on a 4 flat also.

I had the same problem, it was the fuse under the dash by the steering column. It was on a 4 flat also.

I've looked for a fuse, and didn't find one for taillights, only for R & L trailer turnsignals. What fuse did you replace that made the tailights work again? Thanks.

jth7186

TRL PARK Fuse 15 A, Fuse Block - Underhood.

Straight - Line from fuse to connector.

Good Luck.

Idahofox

I'll give that a shot and let ya'll know what happens.

Thanks.

TRL PARK Fuse 15 A, Fuse Block - Underhood.

Idahofox

Good suggestion, Fox. That fuse was blown. Now the bad news...

I replaced the fuse, turned on the headlamps and pop it goes again. I'm going to extrapolate that there is a short in the system because the trailer was not connected when this happened (although I did have a tester in the 7 pin connector at the time so I could verify if the lights would work). Turn signals and brakes are fine (because they are different fuses), but this one is screwed up. Guess I'll have to visit the dealer tomorrow.

Good suggestion, Fox. That fuse was blown. Now the bad news...

I replaced the fuse, turned on the headlamps and pop it goes again. I'm going to extrapolate that there is a short in the system because the trailer was not connected when this happened (although I did have a tester in the 7 pin connector at the time so I could verify if the lights would work). Turn signals and brakes are fine (because they are different fuses), but this one is screwed up. Guess I'll have to visit the dealer tomorrow.

Last summer I was fighting with my utility trailer lights. Ends up that where the trucks wire loom fits into the 7 pin socket (by the receiver) is bent 90 degrees and secured with some ty-tys. I took this all apart and every thing worked, put it back togather and didn't work. The bend messes with the contact alignment in the socket. First place I would look.

Idahofox

Alright, here's the skinny...

Apparently the knuckle-head who put the bed on my truck managed to put a bolt or screw right through the wiring near where the camper harness is (or would be). That caused a short in the system, making the fuse blow.

Tried it out tonight after getting the truck back from the dealer and all is well!

Glad you found it, that was a bugger.


Idahofox

jth7186

TRL PARK Fuse 15 A, Fuse Block - Underhood.

Straight - Line from fuse to connector.

Good Luck.

Idahofox

Thanks for the info. The fuse was blown; installed a new one that didn't. Hopefully the original was just blown from shorted trailer wiring and not a screw in the harness somewhwere! Thanks again.