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Author Topic: Baffled - trailer brake is on permanently  (Read 271 times)


  • Posts: 1
Baffled - trailer brake is on permanently
« on: September 12, 2017, 10:51:40 PM »
I have a 2009 Aliner Classic.  Recently the Elixir power converter died and I replaced it with a Progressive Dynamics 4135.

I used the diagram to hook up all incoming power to the circuit breakers and grounding bars and carefully undid one 12v line at a time from the old converter and reattached them to the new one so that I wouldn't confuse the wiring.

and the fans and lights and recharging all worked again.

BUT......the right hand trailer brake is now on permanently.  (Why only one?  Aren't they both on the same circuit?)

It has nothing to do with the tow vehicle as it locks up even when not connected to a vehicle.  (It also locks up when connected to a vehicle but not to the battery)
It's not the breakaway switch as I disconnected that first thing.
It's not a mechanical problem as it unlocks if I disconnect the battery or pull the fuse on circuit 1. (the blue wire on the old Elixir)
But it stays locked even when I throw the breakers, which makes some sense as they should not be dependent on shore power but would also imply that the converter isn't the problem.

Except that it unlocks if I pull the fuse.

So I am baffled.  I feel like I am missing something obvious but clueless what.

Anyone have suggestions?

« Last Edit: September 12, 2017, 10:59:59 PM by ATC »


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  • Posts: 1492
Re: Baffled
« Reply #1 on: September 13, 2017, 12:04:39 AM »
You probably know most of this but here are some ideas.

The trailer brake is getting 12 volt power from some source.

The circuit that you pulled the fuse to stop the brake from energizing is the logical source, (What you are calling circuit 1).

The fact that it also came on when plugged into a tow vehicle might indicate that it is back feeding or grounding a hot circuit.

The fact that the wire you hooked up is blue is also a clue.  Blue is the standard color code for the brake circuit.

The brake circuit is wired in common so both sides of the brakes should come on if the power is applied.

This might indicate that the problem was caused by somehow hooking power from the convertor to only the one side of the brakes.

Maybe some of this might help you troubleshoot the problem. 

I would start with tracing the power either back from the brakes or forward from the fuse.

The easiest way to do this is with a 12 volt test light.

The condition that you describe is exactly what might happen if you connected a wire directly from a 12 volt source, (the convertor feeding battery power or charger power) directly to only the one side brake with the other brake not getting power because of a (break ? in the wiring between the two brakes.

Normally the convertor or even the trailer battery does not provide power to the brakes.  They are powered by the tow vehicle.  The only exception is powering the breakaway switch.

Good Luck and welcome to the Forum.
« Last Edit: September 13, 2017, 12:35:02 AM by HueyPilotVN »
Bill Waugh
40' Country Coach DP
2 Jeep Commanders
Mustang Bracket Race Car
Retired from the road to Lake Havasu after 35 years on the road