Trailer brake light not working - FIXED

[mrgreetis]

Moderator, please move this if in the wrong place.

I have a 2012 Keystone Sprindale 179QB and I am having a problem with my passenger side brake light not working. I changed bulbs with the driver side and same issue – passenger side not lighting. I tried the turn signals, tail lights, 4-way flashers and both filaments light with at least one of the combinations. Because of that I don’t think there is a problem with the socket wiring or the ground.

I have a 7-pin tester that plugs into the truck connector and when I depress the brake pedal, the LEDs for the driver side turn and brake both light, but not the one for the passenger side turn. I am thinking the one labeled brake is for the trailer brakes themselves.

Does the brake light power come through the wire for the turn signal and that on braking both turn signal lines are energized (solid light)? Or does it somehow come from the brake controller? If on the turn signal line, does that mean that the problem is in the truck wiring? It is a 2004 Silverado 1500.

I have been referring to the Etrailer dot com trailer wiring diagrams to help.

Thanks for any input.

[mrgreetis]

Roo, Those are the ones I treated and the one was the problem. I found them early, removed and wiggled them, but that was not enough by itself.

[RooDude09]

Believe it or not those 2004 silverados have separate fuses for the trailer turn signals. Went crazy over trying to figure out why my trailer light on one side wasn't working when it was just a blown fuse. Figured it was the wiring in our 1985 pop up we had but nope.

[mrgreetis]

Thanks for all your input on this. It is fixed. Caig DeoxIT is your friend.

I had already found the fuses for the trailer turn circuits, removed them, and tested them for zero ohms. So I figured it was the truck’s wiring. Not something to trace down on 100 degree days so I waited until today. Only 84 when I went to look at it. I was able to disconnect the connector from the truck wiring to the 7-pin jack for the trailer and checked that out. Comparing the response for the left vs right, I found the right was still not working correctly. Using a test light on the pin for the right turn signal, the bulb was only dimly lighting when brake was applied. For the left turn it was bright. That meant it was in the truck somewhere.

Not wanting to trace wires, I decided to recheck the fuses for the 2 lines. I pulled them and used the test light to check power to them. With the brake applied, one side of each fuse socket had the test light shine bright, so voltage was getting to the fuses. I recently got a small kit with Caig’s products recommended by Mexicowanderer and Landyacht so I thought I’d try DeoxIT in the fuses. I had already tried just pulling the fuses and reinserting and wiggling them with no effect. I used a swab to wipe down the fuse contacts and the socket, waited a few minutes and reinserted the fuses. I put in my LED trailer plug tester and the correct lights were lit when applying the brakes. Just to make sure, I hooked up the trailer plug and the lights were finally working correctly. I never thought the fuses might be the source of the bad connection.

Anyway, things are looking good but you can be sure I will be closely watching the lights. And getting a spray can of the DeoxIT. Thanks Mex and LY!

[prichardson]

My money is on a bad ground or passenger side turn connection at the 7 pin connector or wiring to it on the TV.

[Vulcan_Rider]

cyntdon2010 wrote:
before you over haul your camper, spray some wd40 in the holes and let it drip dry. it might be a poor connection

Yes I know it's probably worked for you before but.........
WD40 is NOT good for applying to electrical connections, nor a lot of other things either. Just ask any gunsmith.
A good flushing with alcohol is much better.

[Hank85713]

check your book for a FUSE. Son tried to use a trailer I had and lights would not work. Thought I had issues since I had done some work on the trailer and may have pinched/cut a wire. Anyhow I hooked up a battery and played with the connections and all were ok. Turns out he had blown some fuses that we did not know about. Check your owners manual, this was an 04 ford F150.

[cyntdon2010]

before you over haul your camper, spray some wd40 in the holes and let it drip dry. it might be a poor connection

[BB_TX]

The brake light and the turn signal light are the same wire from the truck, same wire in the trailer, and same filament in the bulb. As well as for the 4 way flasher for that side. If the brighter filament comes on with the brake and the 4 way flasher then the trailer is ok. Testing with the tail lights off only one filament (the brighter one) should illuminate. With only the tail lights on, only the dimmer filament should illuminate.

If it works with the brake and not the turn signal I would suspect something within the turn signal flasher circuit.

[Vulcan_Rider]

mrgreetis wrote:
. I tried the turn signals, tail lights, 4-way flashers and both filaments light with at least one of the combinations. Because of that I don’t think there is a problem with the socket wiring or the ground.

Unless you are looking at the bare bulb and comparing the brightness to the other side, you can't be sure that you don't have a ground problem because sometimes it "finds" a ground through the other hot wire and lights both filaments at the same time.

That often happens when the outside shield ground part of the socket gets corroded, or the notch where the ground nub on the bulb makes connection.

[enblethen]

Power to the lights come through with the turn signal.
Do you have red or amber turn signals on the TV? Would be good to know what kind of TV. If you have amber turn signals there should be a 3-2 converter mounted on TV, somewhere.
Wiring will vary somewhat on different TV's.
If you have red, you could have bad connection. Check the junction box on tongue of trailer. Check the trailer connectors.