All Trailer Lights Work Fine Except Brake Lights Will Not Work
Updated 06/25/2024 | Published 04/10/2016
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Question:
Everything works but the brake lights, what did I do wrong? I doubled up the white ground, put brown on Brown, green on green, and yellow on yellow but brake light fail to work. Any suggestions? Thank you.
asked by: Rob C
Helpful Expert Reply:
On a trailer the brake lights and turn signals operate on the same wire/bulb. So, it is odd when the turn signals work, but the brake lights don't. There are 3 possible causes for this that are more likely than any of the other possible causes.
First there could be a problem on the vehicle side. Use a circuit tester such as # PTW2993 to test the vehicle side trailer connector while someone steps on the brakes in the tow vehicle. If there is no power on any of the pins for this test then there is likely a blown or missing tow package, stop light, or CHMSL fuse on the vehicle.
If there is power, then the issue is on the trailer. A bad ground can cause this problem. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light but can show up any time.
Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.
The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.
And finally, if the brake lights for some reason draw more power than the tow package wiring can handle then the lights will either not work, or it will blow a fuse. If they are drawing too much power, then switching to LED lights will solve that problem because they draw a fraction of the power compared to incandescent lights.
I have included a link to our help article on troubleshooting wiring for you.
Carl B.
5/10/2020
I read the above reply by Michael H and followed his suggestions. I sincerely appreciate his insight and mentioning a possible tilt bed because that never crossed my mind although it was exactly the issue with my trailer. Problem resolved. Thank you Mr. Michael.
Jessie E.
6/1/2020
I bought a magnetic trailer light kit so I didn't have to wire anything and all the lights work except the breaks I've tested my 4 way and it says everything is working but the lights will not light up when I push the brakes
Chris R.
6/4/2020
Dave D.
7/8/2020
I have a 1993 Colman/Fleetwood pop-up. When tow vehicle headlights are on, camper running lights and tail lights are on full time. No brake or turn signal lights. When headlights are off, I now have brake and turn signal lights. Bulbs are basic double pole. (1157) Is this right? Doesn't seem to safe for night driving??
Chris R.
7/13/2020
Allen
8/5/2020
Have trailer isolation Honda goldwing 2016. Isolater is put out by electricalconnection. All lights work including flashers but no brake lights tested 5 pin plug at pigtail on bike. Blinkers flashers running lights all work but brake. Did I do something wrong?
Chris R.
8/14/2020
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Adapter 7-Pole to 4-Pole and 5-Pole
- Custom Fit Vehicle Wiring
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Jake W.
4/11/2020
Working on a stock trailer. I have all lights but brake lights, the brakes work and all just the brake lights dont work. I have power at the plug on the truck.