Troubleshooting Trailer Brake Lights Staying On After Installing Tekonsha ZCI Wiring Harness

Updated 11/07/2017 | Published 11/06/2017

Question:

Hello, I purchased Item # 119250KIT ZCI Circuit Protected Vehicle Wiring Harness w/ 4-Pole Flat Trailer Connector and Installation Kit for my 2008 Audi S4 sedan as recommended. I have installed but am having problems. The brakes lights on the trailer are on all the time, even when the car is off. Both blinkers do work. I also have used a 4 way flat circuit tester. When plugged in the brakes test as on all the time, even with the car turned off. The blinkers work, but the taillight tester does not light up. I have tried with the STOP connected to the black and red wire and with and without the TAIL brown connected to the grey and red wire. I appreciate any help you can give.

asked by: Chris

Expert Reply:

The fact that the brake lights on your trailer are staying on all the time indicates a possible short somewhere in the vehicle or trailer wiring. Although it's pretty unlikely with the connector being new, I recommend first checking the connector at the rear of the vehicle for any dirt or debris that might be causing a short.

If the connector looks fine, I recommend moving to the vehicle wiring harness.

The Tekonsha ZCI Circuit Protected Vehicle Wiring Harness # 119250KIT is particularly sensitive with regards to the initial setup and installation process. It needs to be followed exactly for proper operation. Keep in mind that the magnetic sensors in the kit are directionally sensitive. I recommend checking to make sure that all of them are clamped in the correct orientation, as it's possible that a single magnet may have been clamped in the reverse orientation, which can lead to the issues you hare having. Specifically, check the red sticker/stop magnet on the harness to make sure it is installed correctly.

Please let me know if you are unable to locate and resolve the issue and I will be happy to look into this further.

expert reply by: Chris R