unexpectedbill

Yes, the service brake lights do work when the pedal is pressed. Someone may well have replaced the parking brake switch in the dash with another. I did look around behind that part of the dashboard for any wiring that might have gone to the control, but I did not find any.

I will try to get some pictures.

Hello all...

I have a 1989 Mack R690ST model truck that was converted into a grain hauling truck with a dump bed. All the time I've owned it, the parking brake indicator light has never functioned. I've recently been looking in to why that might be, and have confirmed that the bulb is good and that there is power coming to it. In going through the circuit, and looking at some of the other warning lamps (low air pressure) it appears that the bulb grounds are what is being switched.

I've had no luck so far in finding the actual switch, assuming it still exists. There's no doubt that someone has been goofing around with the wiring on this truck over the years. I inquired at an area Mack Truck service facility and dealer, but they haven't been able to help me. Web searches haven't produced anything useful either. I am very much hoping that someone here could point me in the right direction.