Electric brake question

[RRTrick]

Just looking for a little insight into the electric brake setup. I was under the unit checking on something else and noticed the wires coming into the left side of the axle to the brake drum but on the right the butt ends from the electric brake were not connected to anything. Is there some conduit down the center of the axle that bring wires to the right side or do I only have power to the left side.


Thanks for any insight you can give me

[Frank G]

All the wires coming out of the brake backing plate(s) must be attached to the trailer brake wires. One is a ground wire the other is a power wire from the brake controller. The ground wire must be routed through the electrical plug and properly grounded to the truck.

[LHaven]

As I understand it, you are asking whether the wires to the LH brake are designed to "flow through" the axle to the RH brake, or whether the brake wires on the RH side that are hanging loose were supposed to be connected to something. I would assume the axle theory is low probability.

I'd say the most direct way to determine whether you have a problem is to hook up the tow vehicle to its pigtail, have someone apply the brake, and listen next to the wheels. You should hear the same hum from the RH wheels as you do from the LH wheels. If you don't, bring it back to your dealer and have him fix it.

[chuckster57]

As a rule the power for the brakes will exit the underbelly on one side ( drivers side is most common). At that point the DS backing plates and the wires to the PS brakes are all connected.

The PS brakes are hooked up to the wires coming out of the axles. The axles are tubes and the wire is carried from the DS to the PS through the center of the axle.

Easy way to test is to jack up the axle and pull the break away pin. When you spin the tire it should lock up. If it doesn’t, then it’s time for further diagnosis.

[JRTJH]

RRTrick,

Yes, the wires run through the hollow axle tube from the "connected side" to the "looks like it's not connected side"....

Essentially, there are two trailer brake wires, a 12VDC positive and a 12VDC negative (ground). That wire typically runs along the roadside trailer frame rail, branches at the forward axle and goes to that wheel. The connector at the axle runs through the tube to the curb side brake. The "main brake wire" runs from that branch to the rear axle where it does the same thing, through the axle tube to the curb side.

The first is a diagram of the wiring as it should appear, the second is the "curb side" which is connected to the wires inside the hollow axle tube and the third is the "road side" which is connected to the trailer brake wiring from the umbilical connector. In that photo you can see where the wire goes into the axle tube to travel through the tube to the curb side.

[travelin texans]

If you've ever had a tire blow out those wires a usually the 1st thing ripped lose.

[Blackrock]

On my 5th wheel the wiring for the brakes comes down the left (drivers) side and connect to the LH brakes and the wiring is routed thru the axle tube to the RH brake.

[RRTrick]

Thank you for the feedback and the really good information and advice. Nice to belong to such good group of folks willing to help one another. We have the unit wrapped up for another month or so but I will certainly take a closer look once we have her out of hibernation.
Cheers

[roadglide]

Originally Posted by JRTJH

RRTrick,

Yes, the wires run through the hollow axle tube from the "connected side" to the "looks like it's not connected side"....

Essentially, there are two trailer brake wires, a 12VDC positive and a 12VDC negative (ground). That wire typically runs along the roadside trailer frame rail, branches at the forward axle and goes to that wheel. The connector at the axle runs through the tube to the curb side brake. The "main brake wire" runs from that branch to the rear axle where it does the same thing, through the axle tube to the curb side.

The first is a diagram of the wiring as it should appear, the second is the "curb side" which is connected to the wires inside the hollow axle tube and the third is the "road side" which is connected to the trailer brake wiring from the umbilical connector. In that photo you can see where the wire goes into the axle tube to travel through the tube to the curb side.

Your saying there is positive and negative. When I installed new brakes there is 2 wires on each wheel hub , I didn't know the wires could get crossed so long as there is voltage going to the magnic.

[chuckster57]

The wires at the backing plates aren’t “polarity” sensitive, the ground is in the Junction box IIRC. The two wires allow the positive to “pass through” the magnets.

[JRTJH]

Originally Posted by roadglide

Your saying there is positive and negative. When I installed new brakes there is 2 wires on each wheel hub , I didn't know the wires could get crossed so long as there is voltage going to the magnic.

Most RV braking system electromagnets are not polarity sensitive, BUT like an incandescent light bulb (also not polarity sensitive) there MUST be a return line for the current to flow through the light bulb or it won't light. It's the same with the electromagnet in your brakes. So without two wires (in the current design) there would be no braking action.

There are some electric braking systems that are polarity sensitive, but it's typically the anti-skid, modulation system on those brake systems that is polarity sensitive. I've never seen that type brake system installed on an RV, typically they're used in aircraft and other "high tech" items. I'd suspect that as RV's evolve and anti-skid/anti-sway systems are developed for RV's, those types of braking systems (polarity sensitive) will begin to be used, but for now, the braking systems are "basic electromagnetic brakes" and are not polarity sensitive.

[dsjones21]

Had a blow out while back and trying to make sure that braking system is good. I can’t identify where this one wire should go. All other connections look good.
I’m assuming this is either a ground, or the wire that should connect over to the rear axle, which is where the trailer power is coming from.

[dsjones21]

I pulled down the skirt and do see that the trailer line (blue) is spliced into in the area of the wheel, but doesn’t look like it would have been ripped out from here. Am I wrong and if so, which splice would I go into?

[chuckster57]

Originally Posted by dsjones21

Had a blow out while back and trying to make sure that braking system is good. I can’t identify where this one wire should go. All other connections look good.
I’m assuming this is either a ground, or the wire that should connect over to the rear axle, which is where the trailer power is coming from.

Hard to see your pic on my iPhone but it’s fairly straight forward as far as brake wiring. 2 wires not polarity sensitive so you can hook them up any way.

2 wires from brake circuit, attach to 2 wires coming out of the backing plate. If there is 2 wires going to the other side they get attached.

So on one side you will have 3 PAIRS of wires at each wheel. Other side will have one pair on each wheel. Make sense?

[dsjones21]

Is that rule true for both axles? On rear axle I have the 3 and 2 as you speak of, but in front axle I have 2 pairs on each side, with this random white wire in one of the nuts. I figured at least this one wire needed to connect into the harness (blue wire) to make that axle work.

[chuckster57]

It should the rule as far as I know. There will be lots of other wiring running in the underbelly. Unless the brake wires are faulty in the front axle and someone ran a new set under the coroplast I have no idea what that rogue wire is. Can you trace that wire back?