Turn Signals but No Brake Lights on Trailer tail Lights

Updated 08/10/2020 | Published 03/27/2015

Question:

The right side on the back works but not properly. There is not brake lights but the turn signal works but instead of it being in the top bulb it is in the bottom. I am just confused.

asked by: Ryan

Expert Reply:

Any time a trailer has turn signals that work but not the brake lights it can be an interesting situation. This is because the brake lights and turn signals on trailer tail lights are on the same circuit. In this situation it is almost always a bad ground connection.

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.

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.

If the wrong bulb is lighting up it is likely just that the turn signal/brake light wire is attached to the tail light running light wire and the running light wire is attached to the trailer turn signal/brake light wire.

expert reply by: Michael H

Willie

7/31/2020

On my trailer stop lights don’t work but when I push down on the pedal lights come on, both of my turn signals work? I changed the cable. I need to know what fuse to change in my cascadia ??

Jon G.

8/10/2020

So you're saying that your turn signals come on when you press your brake pedal I take it. Do your brake lights come on when you use your turn signals? You may need to check the installation of your wiring harness if your vehicle has separate stop and turn signals.