How to Change a Lawn Mower Solenoid

A solenoid is an electrically operated switch that connects a battery with a starter motor. On lawnmowers, the solenoid activates when you turn the ignition switch to the "Start" position. The solenoid then switches the battery power to the starter motor, which begins to turn the engine for ignition. When a solenoid fails to operate, you must replace it with a new one. You can change the solenoid on your lawnmower with a few tools and basic do-it-yourself skills.

Adjustable wrench
Paper
Pencil

Instructions

- 1
  Disconnect the negative (-) battery cable clamp from the terminal post. Loosen the clamp nut by turning it counterclockwise with an adjustable wrench. Twist the clamp from side to side while pulling it up and off from the post.
- 2
  Locate the solenoid on your lawnmower. The most expedient method is to follow the positive (+) battery cable. It is connected to the solenoid.
- 3
  Draw a sketch of the solenoid as you see it using paper and pencil. Indicate the position of the various wires, their color and their location on the solenoid.
- 4
  Remove the two large gauge wires on either side of the solenoid. Turn each of the terminal nuts counterclockwise with the adjustable wrench and pull the wires off from their respective terminals.
- 5
  Disconnect the smaller gauge wires from their terminals with the adjustable wrench.
- 6
  Remove the solenoid mounting bolts with the adjustable wrench.
- 7
  Install the new solenoid in position with the two mounting bolts. Tighten the bolts clockwise with the adjustable wrench.
- 8
  Attach the small gauge wires to their correct posts and tighten the terminal nuts. Refer to your sketch for the proper positioning of the wires.
- 9
  Connect the two larger wires to their respective terminals and tighten each of their nuts.
- 10
  Connect the negative battery cable and tighten the clamp nut with the adjustable wrench.
- 11
  Start the engine to test the solenoid. Account for each of your tools prior to starting.

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