Why Does a Craftsman Tractor Seat Safety Switch Cause a Shutdown When the Clutch Is Disengaged?

Operator Presence Control Switch

• The seat switch is a spring-loaded “normally open” switch that overrides the ignition circuit. When the operator sits in the control position, his body weight depresses the seat switch control plate, closes the contacts and completes the ignition system circuit. Once the circuit is closed, the operator can start the engine with the ignition switch. If the operator leaves the seat, stands up, or gets dislodged accidentally, the engine stops, preventing possible injury caused by rotating mower blades.

Parking Brake Override Switch

• The parking brake override switch allows the operator to leave the seat for jobs such as emptying the grass catcher without stopping the engine. This is done by depressing the clutch and setting the parking brake. Doing so deactivates the PTO and stops the mower blades from turning. It also activates a second ignition system override switch wired in parallel and designed to bypass the seat safety switch and keep the ignition circuit closed under these conditions.

Anti-Reverse Mowing

• Since mowing in reverse is a dangerous operation for a novice operator to perform, once the reverse gear is engaged, the second ignition circuit override switch is activated. This disengages the PTO and prevents the blades from turning. However, an experienced operator willing to take the risk can override this function by manually setting the ignition switch to the secondary counterclockwise override position. Doing so keeps the operator presence system working and allows the PTO to function normally in reverse gear while the seat is occupied.

Incorrect Parking Brake Operation

• Should the operator disengage the clutch and shift into neutral gear without activating the parking brake, the engine will stop as soon as he leaves the seat. If the engine continues to run after the operator vacates the seat without setting the parking brake, the operator presence control system has malfunctioned. This fault must be addressed before continuing. Check the wiring, switches and connections. If there are no obvious loose connections or signs of a burned out switch, schedule a service call from a qualified service center before using the mower.