Trailer lights not working at the truck

[Gene B]

I hooked the boat up Monday and went fishing. I noticed that all I had working was the passenger side turn signal. I checked the plug on the truck and I only have the turn signal there so it's not in the trailer. I have a 2004 GMC sierra 4WD with the tow package. All the truck lights work. I followed the harness to the front of the truck and didn't see any damaged wiring. There are 3 terminal blocks/relays(?) on a support bar back by the rear bumper. Any ideas?



Gene

 

[tony arnold]

I have a vague memory of a secondary fuse block on my 2003 Silverado that controlled only the trailer lights. I think it was in a bizarre place like under the back seat. Owner's manual available?

 

[Chris Owenby]

Hey i have a 03 silverado too and i had a similar problem once and it ended up being my fuses.

 

[Scott Hammer TOXIC]

Call Mac and get a new truck!!:lol::lol:



TOXIC

 

[firedog978]

Gene,



I have an '09 Silverado and had the same thing happen to me last year. There is a fuse box under the hood. That fuse box has specific fuses for trailer lights. One of them went bad. Took me awhile to find it because all other tailight fuses are in other fuse panels. Owners maual should show it.

 

[Marty Klein]

Can't help you finding the fuses. However, fuses rarely go bad on their own. Something in the wiring or the equipment causes the fuse to blow. Some of the trailer lights can still be operable while other trailer wiring might be problematic. Check that trailer wiring.

 

[Jim B]

The fuses should be in the panel thats under the hood on the drivers side just behind the battery. Once you find them and get voltage workign again you will want to take a look at your trailer for sure like Marty mentioned. If you have a blown fuse there is a reason for it and its most likley a wiring short on the trailer.

 

[TOMMY RICH]

Check the plug that goes into the back of the truck. The pins on mine give me trouble from time to time on my 04'

 

[Gene B]

Tox, I didn't call Mac(I went through my dad) but I just bought a new Malibu to drive for work. That is all the help GM is getting from me for a while!

I found the fuse block under the hood so I'll do some more investigating. If there's a seperate fuse for the trailer lights, why is 1 blinker working?

I took the plug apart and everything there looks great.



Gene

 

[Donald Tracy]

I had the same problem with my 2007 Chevy HD and my old boat trailer. It had a wire in the boat trailer frame that had worn through. The only time it would have any problems was when the trailer was dipped in water and made the connection. It was a pain to run down because of where the short was at. Turned out like the others, it was the fuse under the hood that had blown. Part of the lights would work and part of them wouldn't.

 

[firedog978]

Gene,



In the fuse block under the hood there will be two fuses for trailer lights. Left and right. They do not control anything on the vehicle, just trailer lights (when plugged in). According to your OP, you have passenger side lights on the trailer; so, locate the left trailer light fuse in that block. It will be the bad one. The vehicle owners manual should have a sketch of this fuse block. Mine does and that's what led me to it.



As stated earlier, something shorted to blow that fuse. Check the trailer wiring (left side) for any short or loose connection.

 

[Marty Klein]

If you have a swing away tongue, look at the wiring there. That is a great place to get some rubbing and a short.

 

[Gene B]

Thanks for all the info. I did some checking and I had 2 blown fuses. 1 in the the dash fuse block and 1 under the hood. It's kinda crazy how they split things up. :blink: I had a few minutes to look at the trailer and my ohm meter says, you guessed it, a dead short. A quick look at the trailer didn't reveal anything but when I get some time I'll check it further.



Thanks again,



Gene

 

[Scott Hammer TOXIC]

Might be easier to just pull new wires on both sides. Should be done on schedule anyway as far as I am concerned. Should be a 2-3 hour job. Bring your rig to the MVM and I'll take it off the trailer and out for a day while you work on it. Am I a pal or what!!:lol:



TOXIC

 

[Gene B]

LOL It is so good to know I have friends to look out for me!

I'm hoping to get a look at it today. I'll disconnect the lights and see if it's in the wiring harness or the lights.



Gene

 

[Scott Hammer TOXIC]

Good time to update to LED if you havent already.



TOXIC

 

[Gary Hunter]

Just thought I'd add that my 2007 Ford Expedition has separate fuses for just the trailer. Under the hood, dead center in front is fuse block. Pop the top and (in my case) the fried fuse was #12. (25A trailer/parking lights). It had me scratching my head because the truck lights were all good but I had no power coming from truck to trailer on the brown wire and brakes and directionals, on trailer, were fine - just no parking lights. I had no clue that trailer circuits had separate fuses than truck. Hope this helps someone else down the line.