Current flow to brakes

[Argonaut20]

I am fighting brake problems that are likely caused by electrical gremlins. I measured voltage at the back of the truck and found that there seemed to be a constant current flow through the pin that goes to the brake magnets. The flow is on the order of 12.5 volts, ignition off in the truck. Do the brake controllers send a constant current through that pin, or is there a short someplace in the truck/brake controller harness?

Does anyone have a picture or diagram of the wiring for the brakes in a 6 metre Minuet? I have been under the gaucho at the terminal block and it looks like there is a connection there that is likely the breakaway switch tie in to the brakes, but there has been work done on the brakes in the past (Blue wires to the brakes rather than yellow) and there is a possibility that the brakes are miswired.

[dwightdi]

Wiring harness on your truck is messed up. OR Your brake controller is shot OR the brake controller is miss wired. You should not have constant voltage on the brake actuator pin.

[TomW]

Originally Posted by dwightdi

... You should not have constant voltage on the brake actuator pin.

I do not believe that is entirely right.

Brake controllers work by limiting the current to a given load. But the initial voltage will be ~12 vdc. A current-hungry load will then drop the voltage if the current is limited.

Most voltmeters have a high input impedance which means they will not drag down a circuit with any appreciable load. A brake magnet has an appreciable load. I would expect a voltmeter to read 12 vdc at the brake wire pin if nothing else is connected.

A better test of the brake wiring would be to check voltages with the trailer connected to the tow vehicle.

Tom