Trailer brake controller quit coming down 5%

tbeaulac · May 25, 2022

Towing 12,300 lb tandem axle cargo trailer, i managed to pump the brakes enough and gear the AT down but im telling you the pucker factor was pretty tight. Got it off the interstate and into a hotel parking lot.

I got the test light out but could only get 4.9volts on the blue wire to brake controller that I had spliced into the factory harness. I got to a napa and got a new spool of wire, cut and spliced into the blue wire at my 7pin plug and ran it straight to my battery with an inline 30amp fuse. I hooked up the brake controller, reconnected my batteries then I could adjust up to 14v until my helper pressed the brake pedal, then I get nothing on my test light my 30amp inline fuse blew immediately.

If you have read this far and understand this description you will probably conclude I'm a rank amateur at this and you would be correct. So I'm stuck at a hotel and not sure what my next move is to resolve this problem.... can anyone help?

Thanks in advance

1997 F250HD 4x4 7.3L

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Patrick Feeley · May 25, 2022

Is there a dead short in one of your trailer brakes? Does the fuse blow with the trailer disconnected? Cheers!

Tiha · May 26, 2022

Ditto on breaking the circuit down.

When does the fuse blow? Trailer unplugged?
Plugged in?
On brakes only?

If it only blows after you hit the brake pedal then you will probably have to disconnect each wheel separately. Probably have to leave one wheel disconnected or fix it there.

If it blows when you plug it in, you have a short on the trailer, does it have a break away with a battery?

tbeaulac · May 28, 2022

I was in over my head on this so I got it to the closest repair shop as safely as I could. My brake controller and 7 pin wiring is getting checked as well. so trip is postponed a few weeks. But we are safe, my equipment is safe, and all the other drivers on the road are also safe from this disaster in waiting. I'll be updating this hopefully with good news . Thank you

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tbeaulac · Jul 3, 2022

To quickly wrap things up.

1. There was damage wiring found on the trailer that caused one axles brakes to malfunction.

2. The break away battery was not charging properly, causing it to be non functional.

3. Brake pedal switch on my truck was not functioning (perhaps caused by the trailer grounding?)

These items fixed and made 2300 miles without any further problems. I feel lucky to be alive

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