Trailer brakes

I mentioned in another post about the first thing I did when I got our trailer home from the dealer was to pull the wheels and hubs to inspect the bearings and brakes. It’s a good thing I did because the previous owner had neglected to service them properly. The grease seals had failed and there was grease everywhere inside the hubs. Once brake shoes or pads have been exposed to grease they can’t be cleaned or repaired. You can buy the shoes springs and magnets separately to repair the brakes but the best plan is to buy a whole new brake assembly I bought the self adjusting kind, most trailers came equipped without self adjusters, did you know they need to adjusted at least once a year or more?

To replace the brake backing is really not that hard. There’s one electric brake wire coming to each that has to be cut, and then there were 5 bolts to remove. The whole assembly slides right off and the new one back on, torque the 5 bolts (or 4 on some trailers) and re attach the brake wire. The brake kit comes with a waterproof splice for doing that. I say it’s not that difficult but that’s because I’ve already got the wheels and hubs off the check and repack the bearings. And then it all has to be reassembled.

Trailer brake wiring problems

Fast forward a year or two and I’m travelling home from Washington State and just crossed the Grand Coulee bridge just below the dam and the dash lights up saying the trailer brake controller has lost connection with the trailer. I manually test the trailer brakes and they still work… so I pull over and check the trailer’s connection to the truck and re plug it in. The error goes away and we make the 6 hour drive home successfully. Our next trip out is to Whidbey Island and we head out without any issues. But on the way home, trouble is brewing… the warning about losing contact is getting more persistent but the trailer brakes still work. Closer to home it appears things are getting worse, occasionally losing the brakes. By this time we are luckily only a few minutes from home and limp slowly home. Not going anywhere again until the system is 100%.

But is it the truck or the trailer? My first plan is to rule out the RAM 3500 and the integrated brake controller. I thought of taking it to the dealer but first I had another plan. I dug up the old trailer brakes out of the garage and an old trailer wiring harness and wired up the old brakes and put them in the box of the truck. Now the truck thinks it’s connected to a trailer and the circuit can be tested while driving without actually pulling the trailer. A few days of driving the truck around all over the city with no issues proves it must be the trailer, which makes sense because the trailer is about 10 years older than the truck. When I had got the truck home from the last trip I basically had the warning light on constantly.

So now that it’s time to try and fix the trailer I realize I have no idea where the problem could be. Somewhere, the wire is probably worn through the insulation and grounding out. Who knows where and how difficult to find? I learn that it’s only a single 14 gauge wire heading back to the axles and that there are multiples splices under the trailer – exposed to all the things that can go wrong under there. And for each axle, the wire goes through the inside of the axle to the other side. Somewhere, it’s most likely one of the wires is grounding out, or one of the splices had failed. Thing is the warning light won’t come on unless it completely loses contact with the brakes.

The solution!

The plan is to put a terminal block as far forward in the trailer as possible and run one 14 gauge wire all the way back to each brake with only one splice at each of the brake hubs. I didn’t try and pull a new wire through the axle tube either, the wires to the far side just cross over attached to the frame cross pieces. It means there is no longer a single point of failure in that wiring run. Also, it reduces the voltage drop between the truck and the trailer. Each brake draws about 3 amps for a total of 12 amps over about 20 feet. Check that out in this voltage drop calculator, it’s about 12% or 1.5 volts. Changing it to 4 wires means each wire only has to carry 3 amps not 12, reducing the voltage drop. I also replaced the trailer wire pigtail connector at the front in case there was a problem with it. And finally I got some dielectric grease for the pigtail connector to the truck just be sure. It’s been a few years now, even though I never figured out the point of failure the system is all working great now.

TO DO PICS

pigtail

solder joints

terminal block

14 gauge wire