The John Deere X300 has two main safety switches. One switch will not allow the machine to start if the operator has not followed the proper starting procedure and the other will not allow the blades to turn when there is no operator present. The first switch is located under the operator's seat and the second is located under the parking brake. When the switches malfunction, either the lawnmower engine will not turn over or your personal safety will be at risk. Determining the bad switch requires a few short steps. The procedure takes 10 minutes.
Park the lawnmower on a hard, level surface. Sit in the operator's seat and depress the parking-brake pedal on the left-hand side of the front fender. Turn the ignition key. If nothing happens, the parking brake has malfunctioned; go to the next step. If the engine turns over, go to the next section.
Locate the parking-brake safety switch under the front fender on the left-hand side. There are two bolts holding the switch to the frame. Remove the bolts with an 8mm socket wrench. Unplug the switch from the wiring harness. Plug in a new safety switch and reinstall the two 8mm bolts.
Sit in the operator's seat, depress the parking brake, and start the engine to ensure proper installation.
Park the lawnmower on a hard, level surface. Sit in the operator's seat and depress the parking-brake pedal on the left-hand side of the deck. Start the engine and release your foot from the parking brake.
Engage the mower blades by pulling up on the PTO switch on the left side of the steering wheel. Lift yourself off the operator's seat but do not get off the machine. If the engine stops and the blades disengage, the seat safety switch is working properly. If the engine keeps running and the blades stay engaged, the switch needs to be replaced.
Turn off the lawnmower and set the parking braking. Remove the key from the ignition. Flip the operator's seat up toward the steering wheel. With a flathead screwdriver, pop off the seat switch from the bottom of the seat pan. Unplug the switch from the wiring harness. Plug in a new seat safety switch by pushing the switch into place.
When testing the seat safety switch, do not step off the lawnmower until you have disengaged the blades and turned off the engine.