Many lawn tractors have an electric starting system similar to that found on automobiles. A starter solenoid acts as an intermediary between the ignition switch and a starting motor. Current from the ignition switch is sent to the solenoid, which sends a greater current to spin the starting motor. A lawn tractor that will not start may have a bad starter solenoid. Install a replacement solenoid to get your tractor back up and running.
Raise the seat or open the hood to reveal the battery. Loosen the negative battery cable retaining nut with a wrench. Lift the battery cable straight up from the negative battery terminal and push it to the side so that it will not come back into contact with the terminal. Use a back-and-forth twisting motion loosen the cable from the terminal once the nut been loosened, if necessary.
Locate the starter solenoid, which is approximately 3 to 4 inches in length and is usually mounted to the sheet metal firewall under the hood or under the seat near the battery compartment.
Make a note of which wires are connected to which terminal on the starter solenoid. Loosen the retaining nuts from the terminals on the solenoid with a wrench. Lift the wires straight up from the terminals and push them to the side.
Loosen and remove the two retaining bolts on the solenoid with a wrench. Remove the solenoid from the tractor. Mount the replacement solenoid using the original hardware and mounting holes. Tighten the bolts with a wrench.
Mount the cable that comes from the tractor starter motor to the large terminal on the left side of the solenoid. Tighten the retaining nut on the terminal with a wrench.
Mount the cable that comes from the positive battery terminal to the large terminal on the right side of the solenoid. Tighten the retaining nut on the terminal with a wrench.
Mount the wire that comes from the starter switch to the small terminal on the front of the solenoid labeled with an “S.” Tighten the retaining nut on the terminal with a wrench.
Connect the ground wire from the tractor’s frame to the remaining small terminal on the front of the solenoid which is labeled with an “I.” Skip this step if your tractor's solenoid does not use a ground wire, meaning that the solenoid is grounded internally.
Push the negative battery cable back over the negative battery terminal until it is fully seated. Tighten the clamp on the cable with a wrench. Close the hood or rotate the seat back downward.