Trailer brake help needed!!

[phatdaddy]

Squids, not real familar with electric brakes, so all this is a guess. I'd verify that the 7 pin connector is matching the trailer. Do all the lights work properly? That would eliminate 4 wires (right, left, running,& ground). That would leave 3. (Brake, 12 vt constant and reverse). If everything is right on the trailer, verify the truck. We had a new flatbed trailer at work that would tap the brake everytime you turned the right blinker on.

If all that checks out fine, check voltage while under a load. Sometimes those 11.5 's will drop when put to work. Also might try checking without the trailer hooked to truck, this will eliminate any stray grounding through the coupler, which can confuse the issue.

My tahoe only has the 7 pin connector and i had a bad adapter, 7 to 4, that drove me crazy.

Good luck

[oteps]

Sounds like u have a truck wiring problem. If its a new trailer go back to where u bought it and see if they will let u hook up to another trailer to make sure its not the trailer. If u need any info from the truck side let me know, I have a 99 f350. wiring should be similar.

[Destroyer]

They should all be standard Squidder. 7 pin plugs are just like 4 pin plugs. Industry standard wiring. And usually any problem can be traced to a poor ground someplace.

Here's a wire layout of what should be going where. Hope it helps.

[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.