Troubleshooting Camper Shell Brake Light Not Working When Connected to Blue Wire on Trailer

Question:

I am trying to wire a brake light on my camper shell. I hooked up power to blue wire on 7 pin trailer and also the white wire for ground but it didn’t work? I wired the light to a battery and it works so I know it’s not the light . Any help would be greatly appreciated Thank you

asked by: Keith

Expert Reply:

The blue wire on your trailer should be for the brake output circuit to the trailer's electric brake assemblies. We actually don't recommend wiring lights to this circuit for a couple of reasons, however the brake light should still technically work when connected in this manner since the wire will be receiving power with the brakes applied.

What might be going on in your case is that you have a proportional brake controller in your tow vehicle. Since a proportional controller will send back power in relation to your vehicle's deceleration, if you are testing the lights by stepping on the brake pedal with the vehicle and trailer parked, the controller just might not be sending enough power back to illuminate the lights.

You can try using the manual override on your controller instead (which will send back full power regardless of acceleration) to see if this powers the brake light. If this works to power the light then the connection is good and they will work during normal operation.

I do, however, still recommend changing the connection from the trailer's blue wire to the trailer's stop/turn circuit wires instead (which are usually green and yellow). This is because wiring the light to the brake output (blue) wire may lead to a voltage drop by the time it reaches the brake assemblies. You will also get a variance in the brightness of the light depending on the force you apply to the brakes in your vehicle when wired in this manner.

To wire the brake light to the stop/turn signal wires I recommend using the Pacer Performance # PP20-702 which includes a converter to filter out the turn signals (so the brake light doesn't also flash when using the turn signals).

expert reply by: Chris R