Should There be Constant Power on the Brake Wire When the Brake in the TV is not Being Applied

Question:

Should their be power on the brake wire all the time even when the brakes are not applied

asked by: Steve

Expert Reply:

If you are talking about a brake controller, like the Prodigy P3 # 90195, sending a small signal then there is nothing to worry about. Brake controllers like the P3 send a small signal to the connector to check to see if there is a trailer connected.

Now if the brakes on your trailer are being applied without you applying the brake in your tow vehicle then there are a few things you can check. You will want to check the connector on your your trailer and tow vehicle to make sure that there is no corrosion that has built up. If there is corrosion built up (it will look white or possibly green) then that could be creating a connection between your 12V power supply and your brake controller wiring and pushing that through to your trailer brakes.

If that looks good then the next thing you will want to check are your grounds on both your tow vehicle and trailer. Make sure they are secure and connected to bare metal. You can also test the trailer functions with a 12V battery on their own to make sure that the wiring on your trailer is working properly.

The other possibility is that if your brake controller was hardwired the wire that is connected to your Stop Light Switch could be connected to the HOT side that is continuously receiving power. You will want to make sure that it is connected to the COLD side which only receives power when the brake pedal is pressed.

expert reply by: Jon G