You're talking about the air drier, and it'll either be under the hood, on the right hand side of the vehicle, towards the front, or in front of the #2 axle, on the right hand side of the vehicle.
It will be mounted to a pressure port on the service (foot) brake valve
On a 1986 Kenworth truck, the brake light switch is typically located near the brake pedal assembly, mounted on the bracket that holds the brake pedal. It is often positioned such that it is activated when the brake pedal is pressed. If you're having trouble locating it, consult the vehicle's service manual for specific details and diagrams.
the filter is located below the brake system master cylinder. I'm trying to find out how to remove one.
Jammed brake switch or short in the circuit.
On a 2004 Kenworth K104, the brake light switch is typically located near the brake pedal assembly, mounted on the bracket that holds the pedal in place. It is usually positioned so that it activates when the brake pedal is depressed. To access it, you may need to remove any covering or panels around the pedal area. Always consult the vehicle's service manual for precise details and diagrams.
The fuel filter is located on the drivers side under but close to the air filter and the brake master cylinder.
Blown fuse, blown relay, blown light bulbs, short in the wiring system, bad microswitch in the brake pedal... could be any of those.
Anything from a bad wheel speed sensor up to a complete failure of the ABS system.
The Fuel filter is located on the firewall, next to the brake master cylinder and right behind and below the carb.
The fuel filter is located on the firewall, drivers side around the brake resevoir
It is located under the hood below or beside the brake booster.
You push in the yellow brake control valve...