2016 W900 Brake lights staying on.....

If your brakes are not dragging, I’d venture to say you have a switch going bad resulting in a lying gauge and brakes lights being on.

I have a switch that acts up ever so often, low air idiot light and buzzer will be on, but the mechanical air pressure gauge will show 120 psi.

The local KW / Mack dealer printed off the air line schematic as well as the electrical schematic for me on my truck, might give that a try for yours….

 

Good thing about my electrical schematic is, it gives the part number of the switches. When I needed a thermal switch for the fan I called and give them the number and they ordered it….

 

That feeling of success

 

My T600 had the exact same problem every couple of years. Usually after the winter time and especially if the truck had been parked for a few weeks or months. The brake pedal pivots on a steel pin at the bottom. That pin will get corroded and the brake pedal won't come all the way back up when you take your foot off of it. If you work it by hand you can actually tell there's some resistance in it that shouldn't be there. It really doesn't take much depressing the brake pedal to make the brake lights come on and if it's not returning all the way up when you take your foot off the brake lights will stay on. Remove the pin and clean it up with some emery cloth. Clean the holes the pin goes in too. Lubricate it with PB Blaster or whatever you have and put it back together. The pedal will move free-er now. I would almost bet money this will fix your problem. I would try this before messing with air lines, valves, switches or electrical. Marked the pin in the pic below..