This DIY riding mower repair guide gives step-by-step instructions for replacing the brake interlock switch on a riding lawn mower. When working correctly, this safety switch keeps the engine from starting if your foot isn’t pressing down on the brake or if the parking brake isn’t set. If the switch breaks, it won’t let current reach the starter solenoid coil even though the brake is on, and the engine won’t start. If the solenoid doesn’t click when you turn the ignition key, the brake interlock switch is most likely at fault. Watch this lawn tractor troubleshooting video to learn how to test the starting system and brake interlock switch. Replace the brake interlock switch with a manufacturer-approved replacement part.