Testing electric brakes, Update.

Sorry I misread and thought you had put on new shoes. If you have not yet removed a drum for inspection I suggest you do. Especially if you have ez-lube axles with the grease fitting.

Evenly greased shoes are hard to swallow but interior brake linkage frozen by rust, isn't. If they grab and rotate part way the symptoms would be identical to what the OP has described.

Regular brake grease gets a F+ in my experience. A Q-tip dab of Anti-sieze on the backing plate and within the pin to shoe wear area lasts forever.

Our next pull will be January 1. I’ll just see how it goes. It’s less than 100 miles on flat interstate, so I can make it.

Famous last words...

The testing was done by activating the controller manually. I don’t know if the shoes are new, but they could be. Probably not, but they could be.

Mex, I don’t have the tools to DIY. I’d have to call a mobile tech.

Did you check the amps when activating the controller manually? That would be the final step.

If none of the brakes lock up then I am thinking this is normal and as good as it gets. Yes the new shoes may need to wear in a bit and get re-adjusted. I assume with new shoes you had the drums turned or the shoes may take an extended period to wear in. Highway miles don't wear in the brakes very fast. Need some city driving.

Ultimate solution is disk brakes.

Try this...


With a wheel removed, spin on some lugnuts to protect the threads.

You need a long bar to try and turn the wheel

Activate trailer brakes through the controller

Insert the bar and turn brake drum in direction of forward travel

You should actually hear as well as feel the brake assembly "compound" meaning flex rotate and lock up TIGHT stopping your efforts cold. The flex rotate happens within several inches of circumference rotation of the brake drum.

Compound action must be tight enough to lock that brake drum like it is welded to the axle.

I used a long one inch diameter pipe custom cut to fit inside the wheel wheel. The longer the pipe the better and put some muscle into the effort to turn it. Is the same effort needed to rotate the brake drum in reverse?

Point-by point diagnostics...

I got a clamp meter from Amazon for 31 usd. Seems just fine. The Chinese brand name is MeterK, and it’s orange.

Each magnet is drawing 3.0-3.2 amps. The controller readout was 12.5-12.7 amps. So it’s all good electrically, right?

And I’m confident the shoes are adjusted right.

To repeat, at 25 mph, pulling the controller lever won’t lock the brakes. All it will do is produce a bit of a tug on the truck. I don’t feel there is enough braking while driving. It’s possible the shoes are new, but I don’t know.

Next step?

Snowman9000 wrote:
Ok, I’ve got 12.3v output to brakes with the lever pulled, and 10.5a. So it’s a little low, but is it significant?

If the readings were made when the brake magnets were cold then you may have one magnet that is not connected.

have someone hold the manual controller so that about 3 volts is applied. Then listen with ear very close to each wheel.

The prodigy puts out a pulse width modulated voltage at low levels and the magnet will usually sing at a frequency you can hear.

Snowman9000 wrote:
Ok, I’ve got 12.3v output to brakes with the lever pulled, and 10.5a. So it’s a little low, but is it significant?

Now need to see if the amps are getting to the magnets. DC clamp meter is the easy/fast way to verify at wheels without cutting wires.

Ok, I’ve got 12.3v output to brakes with the lever pulled, and 10.5a. So it’s a little low, but is it significant?