Trailer Brake Electrical Issue

[Kies277]

The trailer brakes on my 2015 Crossroads Sunset Trail seemed pretty weak so I decided to look into them. The brakes only have about 1000 miles or so on them, so they are fairly new.

My Tekonsha controller showed just over 13 volts being delivered and 8 amps being drawn. Physical inspection of the brakes looked good, no grease on the drums and everything was adjusted fine.

I checked the wiring and found 13 volts all the way back to the axles in 12 gauge wire. Where the wires then branched off, there was a drop to 9 volts at each tire. The brakes all measured 3.6 ohms resistance each when disconnected.

I ripped out all the wiring from the axle back and ran hot and ground to each tire (STAR wiring) so each tire is independent of each other. I now had 13 volts to each tire, I was feeling good.

I then connected up all the brakes and fired her up. Tekonsha now showed 9 amps being drawn. Brakes still felt pretty weak. There should be quite a bit more amp draw, shouldn't there?

 

[tlmgcamp]

Very well stated problem. I expect to learn from this post as my experience is limited. A couple questions:

1. What are the current and maximum settings at the controller?

2. Did you re-do all grounds also?

 

[Kies277]

The P3 controller is set to the maximum settings and the testing was done with the brake control slider.

I redid the grounds as well.

 

[tlmgcamp]

Ok...I am going to follow this as it is a good topic. I am not an expert but hoping to get the info for someone who might know more.

You said the pads are relatively new. How many years/miles on the magnets? I believe they lose efficiency over time

 

[Kies277]

There brakes were replaced as a unit, not just pads.

 

[Kirk]

The answers to your questions depend on what type of brake control you have. Most newer controls will cut back on the applied current if sitting still as they detect deceleration. I suggest that you start by reading this article on How Electric Brakes Work first. The other thing to remember is that the amount of braking is not just a factor of current drawn. Very likely there is some other issue. At low speeds on loose dirt of gravel you should be able to manually apply the brakes and have the trailer wheels lock at least briefly if someone is watching them.

 

[Kies277]

The Tekonsha P3 does that, however, I am under the impression that using the manual slider overrides that and applies full braking. I hooked up the Fiver to my truck and rolled forward in my driveway with the slider fully engaged and the brakes did not stop the unit. I will do a full road test on Thursday.

I do have an update though. I went out this morning and checked the amps at the trailer side pigtail with a multimeter. When checked between trailer hot 12V and the trailer brake I got 11.5 amps which seems to be right where it should be.

 

[Contributor]

I have on occasion had the same symptoms after the trailer sat for extended time. I suspect that either the magnets or the pads and drums needed a little use before working properly. I can't explain it. At first I drive the trailer in the storage yard and try the brakes manually and they seem weak. I keep doing it over and over and eventually they grip better. By the time I get the trailer home, after normal driving and braking, the brakes are working normally.

 

[Ex-Calif]

How were the brakes bedded in? Lots of folks say you don't have to worry too much about "modern pads" but I think that is BS.

If the brakes weren't bedded in hard they could have been glazed. There are ways to re-roughen the surface but I would guess it's less hassle to replace the pads and bed them again.

 

[Kies277]

I don't remember how, if at all, they were bedded in.

 

[Ex-Calif]

I don't remember how, if at all, they were bedded in.

This article describes disc brakes but the theory is about the same for drums.

https://www.autozone.com/diy/brakes/bedding-brakes

Another thing to check with drums is the wear pattern on the shoes. If the shoe brake linkages and all are not free it is possible for only the leading edge or trailing edge of the shoe to be making contact with the drum.

Brake shoes need to "float" so they can apply evenly on the drum. Bad wear pattern and or binding shoe hardware is fairly easy to identify.

Something as innocuous as improper assembly can cause all sorts of issues.

 

[tlmgcamp]

I seem to remember somebody saying that you should ride the brakes a bit when taking the trailer out for the first time after it sits for a while to clean off any surface rust that may have formed since it last moved. Any wisdom to that?

 

[Gary RV_Wizard]

I seem to remember somebody saying that you should ride the brakes a bit when taking the trailer out for the first time after it sits for a while to clean off any surface rust that may have formed since it last moved. Any wisdom to that?

Well, there is going to be some rust & dirt on the drum or rotor, but it's gonna get scrubbed off the first time or two the brakes are applied. That might result in some "grabbing" or maybe some slippage (reduced braking), so there is some wisdom in doing it in a more controlled manner than just waiting until the first time you need to stop.

 

[Tulecreeper]

Double...

 

[Ex-Calif]

I seem to remember somebody saying that you should ride the brakes a bit when taking the trailer out for the first time after it sits for a while to clean off any surface rust that may have formed since it last moved. Any wisdom to that?

I drive very old classic cars - It's pretty much SOP for me to "brake check" all my vehicles if they haven't been driven for a while.

I learned this one time when I took off in my MGB after a winter and had zero brakes at the first stop sign - grabbing huge amounts of parking brake - LOL...

I don't worry about the surface rust too much. My bike gets surface rust in about a week or so of not riding here in humid/rainy Florida.

One thing I attribute to brake contamination is that often my vehicles will pull right or left until a few brake applications have been achieved.

 

[Hvactech]

Just thinking out loud. When replacing with whole new assemblies, will the RV stop if you were to get the drivers side assemblies swapped for the passenger sides ? Or does it matter ?
I've replaced lots of drum & disc brake pads on cars but never had an rv that ever had a brake problem while I owned it.

 

[Lou Schneider]

Just thinking out loud. When replacing with whole new assemblies, will the RV stop if you were to get the drivers side assemblies swapped for the passenger sides ? Or does it matter ?
I've replaced lots of drum & disc brake pads on cars but never had an rv that ever had a brake problem while I owned it.

Electric brakes work by dragging an electromagnet against the face of the rotating brake drum to generate the force that pushes the brake shoes outward. So yes, the direction of rotation is a critical factor for proper brake operation.