Help finding Short/Open loop in trailer brake system.

[Leichardti]

2004 WW fB200 Toyhauler

The trailer brake unit inside my truck is showing a short or open loop code. My friends truck says the same thing when I plug the trailer into his truck.

The +, ground and all the trailer lights work fine on the trailer.

When towing the truck looses and gains connectivity with the trailer randomly. Physically moving the plug, wire, etc doesn't alter anything.

Multi meter shows connectivity between the trailer brake wire (blue) and the turn signals, running lights, ground, etc.

I have traced the wires from the plug to the brakes and have not found any issues.

Could the issue be were the wire physically connect to the brakes?
Could the emergency brake unit be causing this issues?

Any info to finding the source of the problem would be great.

Thank you for your time.

[Leichardti]

Thanks for all the info, I appreciate it.

[JBarca]

Look for "No 10 awg, Tinned Marine Grade Cable"

https://www.amazon.com/Ancor-Marine-Grade-Duplex-Cables/dp/B000NUYBRK/ref=sr_1_6?ie=UTF8&qid=1494550...

This post may help if you want to clean house.
Independent Brake Wire Feed Upgrade

If you go the 2 wire cable route, you can skip the junction box in the back and run a separate 2 wire cable from the A frame header down each side of the camper. The front of both are joined to the truck 7 wire cable, then run one down each side of the camper to the axles. You are bringing a ground and hot brake wire to the back. For the front axle, just skin the insulation and solder on a pig tail to the front axle brake coil, 3M 33 tape and shrink wrap the pigtail joining section. Then keep the main trunk cable going to the rear axle brake coil. This does not break the cable at the first axle.

This gives to a sound ground and hot wire on each side of the camper and there is no wire in the axle tube or strapped to the back of it. This also helps each brake coil get a direct hot wire and ground and not dependent on any other coils joined like the original setup was.

We just did my sons camper this way. He was able to drop 2 numbers on the gain after we fixed it all up. Well worth the time to upgrade.

Hope this helps

John

[Leichardti]

I believe the issues was were the wire connect at the first brake drum. It gained connectivity when I wiggled the crimp cap around. I will replace the cap/connection there.

Everything else looks good but There seems to be moisture in my axle, I can see it when i pull out the wire a little bit.

Over the next few weeks i'm going to replace all the fuses, circuit breakers, connectors, service wires under drums and at least replace the wires going thru the axles.

A portion of the brake wiring is well insulated, it kind of looks like romex. Does anyone know where I can buy it or wiring that has heavy insulation?

Thank you for your time.

[JBarca]

MFL wrote:
You may have some chaffed wires inside the axle tube, or right at entry hole into tube, causing a short, if you are actually experiencing intermittent braking, as indicated on your controller.

Jerry

I agree, this is very possible on a 2004 camper. The insulation becomes very brittle over time and there is the chaffing going on grounding out the hot brake wire inside the axle tube going down the road. Depending on how bad the insulation is ground off, even the + and - brake wire inside the tube can to short within itself. Do not have to touch the tube.

If you are standing still and the issue is still there, this helps trouble shoot the problem. If your meter has ohms on it, check both the hot power brake wire to ground and also for open loop, check the ground connections for having high resistance. Check the resistance through an actual coil so you know what the coil resistance is. Then when checking the hot wire to frame ground if the resistance is less then the coil itself (which is not a lot) then you know somewhere you have a leak to ground. You may end up breaking the connections apart to isolate the problem.

Corrosion on the frame where the brakes ground at to can cause an open circuit. Also the ground up front where the 7 wire truck cable grounds to. Corrosion is bad news on a brake circuit. The best method is to run a complete ground wire attached where the truck 7 wire ground is at all the way to the brake coils.

Hope this helps

John

PS. If there are any scotch lock connections on any brake wires, get them out of there. That is a problem waiting to happen. These things

[MFL]

You may have some chaffed wires inside the axle tube, or right at entry hole into tube, causing a short, if you are actually experiencing intermittent braking, as indicated on your controller.

Jerry