Weak trailer brakes resolved... trailer charge puzzling. - Diesel Forum

MackE7 · 08-12-2005, 11:26 AM

I finally got around to fixing my trailer brakes. We originally discussed it in this thread.

http://forums.thedieselstop.com/ubbt...art=1&vc=1

I'd reply to it, but it seems to be closed ?

Anyway the problem was totally electrical. First of all, I have the ground wire to the trailer connector attached to the frame of the truck via a big ground lug/stud. It was corroded. The trailer battery charging voltage went from 11V to 13.4V, just by fixing that.

Then I started pulling off the brake drums and checking magnets and shoes. On the front driver's side drum I found the wire going from the brake supply to all the trailer brakes to be almost broken. I soldered the joint and everything works well. My brake current went from 8A normal, 10A max to 13.4A all the time. I can't lock up the trailer wheels, but when I apply the trailer brakes with the emergency button it yanks the truck back pretty good.

My trailer has a lot of miles on it. The shoes are getting a bit thin, but they can run another year until I have time to rebuild them. The magnets are not flat either, but I am thinking they will wear flat now that I've got some current going to them. I bought new magnets thinking I would be replacing them, but they had hardly any wear compared to new ones. They just weren't perfectly flat anymore.

I've still got one unresolved issue. I've got a 0.5 Volt drop on the battery feed wire on the trailer connector cable. The battery charge voltage on the truck connector is 14V with the trailer connected. The battery charge voltage at the junction box in the trailer pinbox is 13.4V. The voltage drop on the ground wire is like 0.1V and the voltage drop on the trailer charge wire is 0.5V. The wire is a decent size, so there must be a nick in it somewhere to cause that drop. I cleaned the contacts in the truck socket with a small file and the voltage stayed the same.

It sure is time consuming to troubleshoot and fix these problems. Now that I know how to do it, it would be much, much faster next time.

I'd like to kick the guy who but the trailer cable junction box INSIDE the the pinbox. I've got a kink in my neck today from trying to work on it in there.

Tail_Gunner · 08-12-2005, 03:25 PM

[ QUOTE ]
I have the ground wire to the trailer connector attached to the frame of the truck via a big ground lug/stud. It was corroded.

[/ QUOTE ]

Where was the ground wire in question located? Was this a factory ground or aftermarket wiring?

MackE7 · 08-12-2005, 03:58 PM

The ground stud was actually a factory piece. It is located on the inside of the drivers side frame rail, half way between the rear bumper and the rear axle. If I remember correctly it is just behind the shock mount.

Tail_Gunner · 08-12-2005, 09:38 PM

[ QUOTE ]
It is located on the inside of the drivers side frame rail, half way between the rear bumper and the rear axle.

[/ QUOTE ]

Thanks for the info. I found the ground you refered to, cleaned up the frame metal, applied a dab of electrical grease to help prevent future corrosion, torqued down the bolt and finally applied some undercoating spray. Come Sunday I'll find out if the trailer brakes work any better.