I have a 20 ft 10k car hauler with brakes on all 4 wheels. The trailer brakes suck. When I first bought this trailer, there was zero trouble getting the wheels to lock up, now, with the brake controller cranked up all the way you can barely feel them.

Last fall, I replaced all the wiring for the lights, I also replaced the wiring for the brakes as well. Still lousy braking. I assumed the trouble was with the truck or the brake controller, that theory was debunked when I used the truck with a different trailer. I failed to turn down the controller, the trailer brakes locked up with a loud screech. Obviously the truck is fine!!!

This is the troubleshooting I have done so far:

I have checked the resistance of all 4 magnets, the lowest measured 3.8 ohms, the highest is 4.2. That falls within every spec I can find.

I used a jump box to power each magnet to measure current draw, all are within 3.5 to 4 amps. Once again, seems within spec. What’s strange is while measuring current draw, each wheel locks up solid and immediately with the battery connected.

I have wired each wheel using 14 gauge wire, with the main brake power feed 12 gauge. I also used WeatherPac connectors at each magnet so I could isolate each wheel for testing. Once my wiring is completed, I’ll repeat the resistance and current draw test at the 7 way trailer plug. While I don’t remember actually testing the resistance/current draw after the wiring repairs last fall, I think I would have done so.

Im very meticulous with my wiring, everything is soldered and insulated with marine grade heat shrink tubing (the kind with glue inside to waterproof the connection). I used a 3/8 bolt welded to the trailer tongue for the main ground wire, the grounds for the brakes are also on this stud.

This has me frustrated. If the truck is fine (as verified with a different trailer) and the magnets test good electrically, and the brakes work mechanically, why doesn’t it work as expected in service?! What am I overlooking?

Brakes are something that needs to work reliably and correctly. I’ll be hauling a heavy car thru the mountains of Tennessee in a couple weeks, I’d like to have the brakes working.

Opinions? Thoughts?? Should I have a anchor on the trailer just in case??

 

What is the shape of your ground between the trailer and the truck?

 

I’m no expert for sure. I’ve owned several 10K lb trailers fifth wheel combos. As I recall, there is a difference in wiring 7 prong plugs - slight but different. Different enough it may affect the signal(s) you’re providing from truck controller and truck wiring to trailer 7 plug wiring harness. I ran into a similar issue years ago it turned I “think” I recall where one wire only (wish I could recall specifically) was wired incorrectly in my truck wiring harness for the fifth wheel trailer. I believe what I’m saying is this. Double check the wiring schematic between the truck wiring harness and the trailer wiring harness. I had my wires incorrectly hooked up in the truck wiring harness plug. Easy thing to overlook and you’d think all are exactly same but found out otherwise.

 

Sounds like glazed pads and or drums to me similar to "brake fade" no graba graba. May just need a turn for some new meat.

 

there is a ground (white wire) wire in the 7 pin trailer plug and socket. The wire/socket on both the truck snd trailer are in good condition.

 

There is a diagram non the trailer plug lid showing the pinout. It’s all wired correctly.

 

OK Well, if you’re positive the pin out on the trailer is identical to the wire ‘signals’ being transmitted by the truck controller it should be correct. My issue as I recall was the signals produced and received were different. But, I was switching between trailers which required a feed for additional pulses to accommodate additional electrical supplies e.g. refrigeration while towing and another ancillary feed. The wiring was different on a couple trailers. Best of luck.

 

Run a temporary ground wire between truck and trailer with some alligator clips to double check the ground circuit. I have had several customers in the past with a problem like yours when Ford started selling trucks with factory brake controllers. We would go for a test drive and the brakes were weak or the trailer disconnect warning would come on. I would have them stop. I would clip my jumper ground wire on and the problem would be gone. Good luck.

 

I had the same problem and found the drums needed to be machined to make the magnets grab. Machine shop wanted as much to surface the drums as it was to replace with new. Worked great after that. I had the same issues troubleshooting.
Good luck,
Rick

 

Can you temp wire some lights in to the brake power and go for a drive? Hit brakes, if the lights light up and it still sucks, you have a mechanical issue, no lights is electrical.

 

I’ll try this. I’m running out of ideas.