I am not getting a display when the truck brake is activated, only if I engage the manual switch. I have a 2005 GMC Seirra with a fact. installed 7 way plug. It had been working fine,then I noticed the display was out when braking.
Expert Reply:
The most probable cause for not getting a display when you apply the truck brake, but getting a display when manually activated is a bad connection in the stop light circuit. I assume since the truck came with a factory 7-Way that you had the brake controller port underneath the dash. The stop light circuit is the red wire coming off the brake controller. Follow the red wire from the brake controller and look for a loose connection or a frayed wire.
I have provided a link to instructions that you may find useful. There is a trouble shooting guide that lists the your problem as a result of a bad stop light connection.
expert reply by: Patrick B
