So I have a single axle 1995 Ford L9000 with an M11 Cummins that I pull a stock trailer with, the trailer has electric over hydraulic brakes, and recently the brake lights on the truck and trailer and trailer brakes quit working off the brake pedal. Everything still works off the trailer brake controller when I hand activate it. I’m thinking it’s an electrical switch somewhere but I don’t really know what I’m looking at. Anyone have knowledge or experience that could give me a place to start?
Tractor pneumatic/air switch for brake lights. Would be a good place to start, located on foot valve or a cab air system manifold. Normally just a two pole switch.
I thank there are two brake air pressure switches. Primary and secondary. Believe they are in front of the fire wall. However I would normally feed those trailer lights off the truck tail lights to a trailer connector. The turn signals and brake lights work properly off the same wire that way. Feed the electric brakes from the controller to the same connector. If you are wired that way look for power to the turn signal switch from a brake switch. Have you checked the fuses?
I remember them on the firewall but didn't the ones with the treddel valve above the peddle have one under the dash. And wasn't thete an issue with aftermarket signal stats. No over riding any advice, just testing old memories
Searching for memories in cob webs myself. Where ever they are should be 2 brake light switches. Power to one side all the time and power to the other when the service brakes are applied. Primary should feed the brake light switch. I thank factory signal stats had 2 different wiring arrangements. One from the Mack dealer might need a couple wires swapped in order to work in an International. Not arguing just the best I remember.
Trucks with air brakes, the brakes lights are paired into the signal system for front turn/marker for tractor tail/turn/brake.