Troubleshooting a Brake Controller Draining a Vehicle Battery When Not in Use

Published 04/17/2013

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Digital Multimeter with 42" Long Test Leads - LED Display

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Question:

I need wiring diagram for a prodigy p2 for a 2006 hyundai tucson. We had it installed and we need to trace it, because it keep drawing the battery dead every 2 days. Can you help us?

asked by: Timothy R

Expert Reply:

It sounds like there is a short somewhere in the system that is drawing power and draining the battery. The brake controller you have should only draw a few milliamps of power when not in use. The most likely shorts are a short to ground and a short to the blue wire.

Start at the brake controller and sever the blue wire leaving enough length to reconnect when finished testing. If everything is shut off, test the blue wire to determine if there is voltage coming through. You can use a multimeter like # PT89ZR if needed.

If there is power, more than a few milliamps coming through on the blue wire, then that would indicate a problem inside the brake controller and it will need to be replaced. You can also check the power draw on the black wire.

If it is pulling more than a few milliamps, then you will need to check the connections on the black wire to see if it is intact. Do the same with the ground (white) wire of the controller. It should be attached to a clean bare metal surface.

If the brake controller checks out, move on to the vehicle side trailer connector. If there is dirt or corrosion in the trailer connector or in the back where the wires attach, this can cause a short to ground or short to brake and be drawing power all of the time.

Since this happens with or without a trailer connected, the trailer is most likely not the problem, but it would not hurt to make sure there is no dirt/corrosion in the connector just to be safe.

I also attached an FAQ article on wiring a brake controller from scratch that should have information on how you installed your controller.