Help, Brake Light Problem - Air Systems and Brakes Mar 21, 2008hello, can anyone help. I have a 1983 mack r model 685. I installed an electric trailer brake unit yesterday, everything worked fine untill today lights are staying on all the time. I traced the problem back to the brake light switch wiring. For some strange reason now the cold side of swichWiring trailer lights with combination tail lightsMay 07, 2015Brake Switch - Fire ApparatusDec 09, 2013Brake Lights - Electrical, Electronics and LightingMar 11, 2008See more results Mack Brake Light Switch Wiring Diagram | Wiring Source Mack Brake Light Switch Wiring Diagram. welcome to my blog here I will show you a little more what you are looking for Mack Brake Light Switch Wiring Diagram below there are some photos and a little about Mack Brake Light Switch Wiring Diagram that you can see and read, hopefully in accordance with what you are looking for.