1. Locate the brake pedal assembly. This is usually located on the floor of the cab, underneath the steering wheel.
2. Look for a switch that is mounted on or near the brake pedal. The switch may be mechanical or electrical.
3. If the switch is mechanical, it will have a plunger or lever that is activated when the brake pedal is depressed.
4. If the switch is electrical, it will have a wire connector that is plugged into it.
5. Once you have found the brake light switch, you can disconnect the wire connector or remove the switch from the brake pedal assembly to replace it.
