Trailering Brake Light Question - Please Help.

[hoytkimbershimano]

Hi All,

 

Finally, I got my 5 posts in and can start a topic. I have an interesting problem here. I recently noticed that I only get one brake light on my boat trailer. I have to use the adapter (Delphi and came with the truck) for the 4-pin style connection.

 

All turn signals work on the truck AND trailer. The running lights (headlights on) work on the truck AND trailer.

 

When I step on the brake though, only one brake light comes on. My dad and I took a meter and checked the voltage at the harness adapter and the brake light that doesn't work gets no voltage when I step on the brakes.

 

Any ideas? I know that there has been a lot of talk about fuses here, but EVERYTHING works except for the one brake light. There seems to be something wrong on the truck side. If this explanation is confusing, someone else is having the EXACT same problem: http://boards.trailerboats.com/cgi-bin/tra...ic;f=7;t=001544

 

I know that the turn signal and brake essentially are the same which is what makes this so perplexing.

 

Many thanks for your help!!!!!

 

I have a 2005 Sierra. Nothing has been done to it. It has the HD trailering package.

 

Let me know if you need more info....

 

Tim

[az'03Silverado]

If there is no voltage at the 7 pin connector on the truck, you may have a blown fuse for that side. The fuse for the trailer lights (brakes, signals, ect) is on the driver's side of the dash inside the door. There's a fuse for the left side and a fuse for the right side. If there is voltage at the 7 pin connector but none at the 4 pin part of the adaptor, then either there's an open inside the adaptor or the contacts may be dirty. Try cleaning them or just jiggling the plug to make a good connection. Hope this helps.

[hoytkimbershimano]

Could it still be the fuse even though the signal is working on that side?

 

Also, last night I tested a different adapter that my cousin uses for his '02 Silverado which has no problems with - same thing. No voltage coming out of the adapter. Today I'll try and check it at the 7-pin connector, but think that it will probably not be working there either. The trailer is fine since when I hooked it up to another vehicle everything checks out OK.

 

It would make a lot more sense if the turn signal on that side didn't work, but it works just fine.

 

Thanks!

Tim

[Jim2002Z71]

Fuse for for both left and right signal and stop lights, had same problem...

[az'03Silverado]

find out anything? I've had those fuses blow before and it's very frusterating to figure out.

[asilverblazer]

I don't think it would be a fuse because then the turn signal wouldn't work. I bet its a problem between the brake light switch and the trailer's turn signal fuse. In other words the trailer (right isn't working, correct?) right stop/tail isn't getting the stop signal from the brake light switch. However, it is getting the turn signal. The fuse would still be good. The left side would still be working fine because it is still getting stop light signal from the switch...

[yfz450dk]

I dont know if this is your problem, but on the 2 trailers that i own, when one light comes on or one is dim there is sometimes a poor ground, check your ground wires, like i said i dont know if this is your problem... sorry

[BCNU]

I dont know if this is your problem, but on the 2 trailers that i own, when one light comes on or one is dim there is sometimes a poor ground, check your ground wires, like i said i dont know if this is your problem... sorry

I agree, check your ground, this is usually the culprit on a problem like this. Good luck hope you figure it out!