There is no brake light switch. There is a brake light pressure censor that is located under the cab where the driver's seat is. T.R.
On the brake pedal itself.
It's attached to the brake pedal arm.
Should be to the left of the clutch pedal.
the brake light switch is an air over elec. switch located in an air block on the floor behind steering shaft
There's continuous power supplied to the circuit. When the switch contacts, it closes the circuit and allows the power to go to the brake lights.
Stuck brake light switch, or a short to power somewhere in the brake light circuit.
behind the panel right in front of the throttle pedal
The brake light switch is not air actuated.
Bad switch, bad wiring, ECM fault. If your jake brakes still work, you can rule out the accelerator position switch. The brake position switch might be reading that the brake is depressed when it isn't.
It's just a weatherpack terminal. Literally a plug and play device.
Short to power in the brake light circuit. Most likely, the fault is in the switch itself.