1. Disconnect the wire from the negative terminal of the battery.
2. Disconnect the wire connectors from the switch terminals.
3. Loosen the switch lock nut and unscrew the switch from its bracket.
4. Check the brake light switch. For a working brake light switch, when the rod is fully extended, the tester readings should tend to zero, i.e. the contact is closed.
5. When the rod is recessed by 4–5 mm, the tester readings should tend to infinity, i.e. the contact is open.
6. Install the switch in reverse order. Adjust the switch position so that the brake lights come on even with a small amount of brake pedal travel.