Brake Madness

[vangoes]

Let me start by saying "electric brakes can drive you mad"! With that out of the way, my primary problem is low voltage at the brakes when hooked to truck. Now here is my confusion. Voltage at truck plug without trailer hooked is 12.4v. Hooked to trailer, the voltage at the junction box in the kingpin is only 7v but if I disconnect the blue wire feed to the trailer brakes the voltage returns to 12.4v. With this low voltage trying to diagnose the individual brake magnets is virtually impossible so I decided to unhook truck and try the breakaway switch route. Now, the voltage at the junction box is higher than the previous 7v but is still only 10.4 volts. If I again unhook the feed to the brakes, the voltage in the junction box jumps to 12.6v, and is the same voltage at the battery. To sum it up, there is voltage drop when ever the brakes are inline.

I decided to test each brake using the 10.4 volts that the breakaway was providing. Here are the results: Voltage 9.2 - 9.6v; Amps 2.3 - 2.5; resistance 3.4 - 3.5 with magnets disconnected and 1.1 - 1.2 with magnets connected. I believe the results are normal and expected considering the low 10.4v to start with. There is no one brake giving results outside the ranges of the others which tells me the magnets are all good.

I also believe the truck controller is good as is provides 12.4v when the trailer is unhooked.

If anyone out there has any suggestions to help me find the problem I would greatly appreciate it.

[bethandkevin]

Take a look at the trailer plug itself. The connections inside could be compromised.

[vangoes]

Thanks Kevin, I have already replaced the plug. It never fit the truck receptable very well so I thought it might be bad connections. New plug snaps in and fits very nicely....but no improvement. At least I have a good fitting plug! lol

[BB_TX]

Check every wiring connection you can find in and around the wiring in the pin box and junction box area. A wire downstream of a bad connection can read full voltage with no current, but drop significantly as current increases. Could also be a wire partially broken inside the insulation, a hard thing to find. Look for crimps or unusually flexible sections of wire.

[Phil P]

Hi

Here are few things you need to know about the electric brakes and the wiring system.

#1 the brakes will be damaged by pulling the emergency pin and leaving it for an extended time. (Ref: Dexter manual)

#2 the controller in the truck will not deliver a full 12 V to the braking system even when set to 10 if you have the new type controller. (Ref: GM Silverado repair manual)

#3 the voltage drop you see when you pull the emergency pin is normal because of the high amperage the brakes are pulling from your house battery. (Ref: ASE electrical training manual)

The way I check my brakes is to take the trailer to a gravel road, have wife watch the brakes on one side of the trailer and at a walking speed apply the brake controller by hand. I do this on both sides of the trailer both wheels should “lock” and slide in the gravel.

If your trailer will pass this test when loaded for travel your brakes are working as good as they ever will.

Phil P

[dieselguy]

Find a "good friend" that will let you plug your fiver into his truck plug ... quick and easy way to isolate truck or trailer question.

[bethandkevin]

quote:Originally posted by dieselguy

Find a "good friend" that will let you plug your fiver into his truck plug ... quick and easy way to isolate truck or trailer question.

Excellent advice!

[vangoes]

Has anyone with a 2012/2013 Dodge tested the brake voltage coming from the truck with trailer hooked up, full brake applied and setting on 10 and not moving. As stated in OP, my voltage at the jbox under this condition is very low. I've sent Dodge a question about the contoller (proportional/delayed???) and what would the expected voltage be under these condtions but I have not received an answer.

[CountryGuy]

There is an update for the brake controllers on the 2012 Rams. I know this since I had it done and the difference in stopping was amazing. Before the update I had the controller set on 9.5 and was not happy with the brakes. After the update I have it set on 7.5 and is perfect. Good luck. Keep us informed of the outcome.

[vangoes]

Al, thanks for that info. I'll check with local dealership on that.