Trailer brake help needed!!

[chart]

Grounds are the most overlooked problem. All your power connections are only as good as your worst ground, grounds between controller and truck, trailer and truck, and device and trailer.

[SkunkBoat]

agree, there needs to be a wired grnd connection (white wire) from truck chassis to plug and from plug to trailer. Some trailer plugs don't pass the ground thru and rely on the connection of the ball & hitch.

and sometimes you have to run a ground wire all the way to the studs of the lights (or brakes) and not rely on the trailer chassis as a ground.

A common symptom of bad grnd is that your lights appear to work until you turn on your parking lights and then your brake lights don't work. This is because the circuit is using the 0 volts on the parking lights as a return until you put 12v there, then it doesn't work.

Some vehicles have yellow turn signal lights separate from brake lights. They require an electronic adapter because trailers use the same lamp filament for brake and blinker. When these adapters stop working, weird stuff happens.

[3 Squids]

Found the problem. The blue wire in the factory harness is grounding out somewhere between both ends. According to the FSM it doesn't have any splices in it just a plug at the firewall harness. I cut the blue wire coming out of the control box and connected a long jumper wire to it then ran the jumper wire straight to the trailer and sure enough the brakes work fine. So for a quick fix I ran the jumper along the frame to the back of the receiver plug and all is normal now.

[Destroyer]

Originally Posted by 3 Squids

Found the problem. The blue wire in the factory harness is grounding out somewhere between both ends. According to the FSM it doesn't have any splices in it just a plug at the firewall harness. I cut the blue wire coming out of the control box and connected a long jumper wire to it then ran the jumper wire straight to the trailer and sure enough the brakes work fine. So for a quick fix I ran the jumper along the frame to the back of the receiver plug and all is normal now.

That would make sense since the blue wire is the one that goes to your brakes. Glad you found the problem Squidder.