How to Use Circuit Tester to Find Brake Light Switch Wire for Brake Controller Installation

Updated 06/18/2019 | Published 06/15/2019

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Question:

In the article it states to refer to the video for the stop switch connection. I did not see a link for this video anywhere within the article. question 10200. Thanks

asked by: Bob B

Expert Reply:

The video you referenced in your question about trailer brake controller installation is linked for you. At the 7:20 mark our installer does begin the process of identifying the brake light switch wire that will connect to the brake controller's RED wire. He used a circuit tester like # PTW2992 and # PTW2993 to probe the wires at the brake light switch to find the one wire that carries 12V power ONLY when the pedal is pressed.

There will be other wires for other functions clustered in that same general location above the brake pedal, so it is important to test those wires to find the one that carries power only when the pedal is pressed. A wire's color is not a reliable way to determine the function carried on it.

expert reply by: Adam R