Why is a Relay Needed When Installing a Tekonsha P-3 Brake Controller # 90195 on a 2008 VW Touareg

Question:

Hello, Installation diagram for the 2005-2008 VW Touareg shows a relay. Why is it needed? Many thanks!

asked by: Robert L

Expert Reply:

When installing a Tekonsha Prodigy or Tekonsha P-3 Brake Controller, part # 90195, on a 2005 to 2008 Volkswagen Touareg, a relay like part # A-715, is needed to prevent an erratic display on the brake controller.

Apparently to activate the lamp out bulb on your vehicles dash a test pulse is run through the brake light output wire. This test pulse will cause problems on the brake controller unless a relay is installed inline.

It will need to be installed on the red brake wire between the brake controller and the brake lamp signal on the factory brake controller connector on the vehicle.

I am including a link to a technical bulletin regarding the relay when installing a brake controller on a Volkswagen Touareg.

expert reply by: Jeff D