7 pin plug for trailer lights

[blatta1999]

i am having an issue. I have plugged my 7 pin plug from my camper to test my lights. I have all lights except my driver side brake light on the camper. I hooked my truck to it as well just to make sure it wasn't the camper and they all worked. So I am assuming it is the 7 pin. Has anyone had to troubleshoot this as far as which wire is which. I am thinking it may be easiest to tap a wire off the driver side tail lamp and run it to the 7 pin. Thanks for any info.

 

[Fless]

If the DS turn signal doesn't work either, check the in-cab fuse. Trailer circuit is fused separately. Sorry this diagram isn't going to be very clear, but the two fuses within the red circle are for the trailer brake lights and turn signals. DS is the top one in the circle.




I'd be interested to know if that's the fix.

 

[blatta1999]

I guess I could've mentioned that. Drivers side turn signal and actual tail lamps work when lights on the Tahoe are on.

 

[Fless]

As long as the DS turn signal works, it seems like the brake light ought to work, too. I'd be checking the socket pin to see if there is 12v when braking, and it's making only intermittent contact. Might be able to bend it just a little for better contact? Even though the other lights work okay, I'd also probably be checking and cleaning the ground from the 7-pin to the truck frame, making sure it's great.

 

[Fless]

One other thing that I'm seeing from other sources is that this can be caused by the flasher unit that is behind the fusebox at the lefthand side of the instrument panel. Form what I read it controls some brake light functions.

 

[Archer04]

I would test the brake light first at the socket first, also make sure the bulb is seated correctly and is making full contact. I am sure you have done that already, but might be a good idea to check the ground wire at the socket too and under the trailer to make sure you dont have a break in the line some where. Had a small dog chew on a wire just above the axle of my trailer, and it took a while to find it, and was a slight pain to repair it. Then move up to the 7 pin connector if you have done all that, that way you will know it isn't something in the trailer and can trouble shoot the next part. Also have you considered swapping out the 7 pin connector with another one and seeing if that fixes the problem, could be something in the connector plug itself.

 

[Parthery]

Test at the socket first. Then check your plug side on the trailer.

Also - are you testing the lights with the trailer hitched to the truck? If you aren't, you may have an issue that shows due to the ground not being complete all the way to the trailer.

My boat trailer has a 5 way flat. I use a 7 to 5 adapter. They don't last real long and when they go it shows up in the form of some lights not working.

 

[blatta1999]

Trailer was hitched up. Turn signal works and lights but not brake light. I hooked my pickup truck to it and all lights work as they should so I assume it is with the 7 pin plug or somewhere on the Tahoe.

 

[W8TVI]

Trailer was hitched up. Turn signal works and lights but not brake light. I hooked my pickup truck to it and all lights work as they should so I assume it is with the 7 pin plug or somewhere on the Tahoe.

Like @Fless showed in his post, the brake lights and turn signals are the same wire and bulb on standard trailer wiring.

I would suspect something in the Tahoe other than the 7-pin plug, seeing that the turn signal works.
But like everyone else, check your grounds!

 

[04 Yukon SLT]

Hello Everyone

I'm new to this forum. I have a 2004 Yukon SLT that is having the exact same problem. I was hoping someone found a solution.