What Is a Mower Solenoid?

Lori Kilchermann

A mower solenoid is an electronic device used to engage the mower deck of a riding lawnmower. Used to activate an electronic clutch, the mower solenoid is intended to serve not only as a means of switching the mower deck on, it is also used as a safety device in the event of a mishap. Many lawnmowers not only wire the mower solenoid into the mower deck, but the solenoid is also wired into a safety switch that can disable the mower deck in the event of an emergency.

Woman holding a book
Woman holding a book

Much like the air conditioning pump in an automobile, the mower deck on most riding lawnmowers utilizes an electronic clutch to power the mower blades. The clutch allows the drive belt to operate freely, without driving the mower blades until the operator switches on the mower solenoid. When this happens, the belt is powered and no longer is allowed to ride on the free-wheeling pulley. The blades begin to spin and the mower is able to operate as intended. The mower solenoid will commonly switch off when the mower is placed into reverse, however, a manual override is usually used to allow the mower to be operated when in the reverse gear.

Commonly called a dead man's switch, a safety switch mounted under the operator's seat is routinely wired into the mower solenoid and used to switch the mower blades off in the event the operator becomes absent from the mower's seat. This device is intended to prevent injuries from occurring should the operator become incapacitated and fall off of the mower for any reason. Some mower deck designs also incorporate an emergency shutoff feature on the mower deck in case it becomes bogged down or overheated for any reason. This is intended to protect the belts from being damaged due to slippage and burning, as well as to protect the clutch from heat damage.

The most common method of wiring a mower solenoid into a mower's electrical system is to wire the solenoid into the on switch, the shifter mechanism and the seat safety switch. Another recipient of the solenoid's wiring is the clutch pedal. On mowers so equipped, the manual override switch is also wired into the mower solenoid to allow use of the mower in reverse gear applications. This switch typically requires the operator to depress an override button and hold it down the entire time the mower is engaged in the reverse gear.

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Discussion Comments


@Animandel - What is causing your lawn mower to not start the first time could be related to the starter. I guess that is the obvious answer, so maybe you have tried that.

The carburetor is also another of the usual suspects. Something as simple as a little trash in the carburetor or water in your gas line are both possible answers to why your mower won't start.


@Animandel - The trouble you are having getting your lawn mower fired up could be caused by a bad solenoid, but there are a long list of other things that could be at the bottom of your problem. Unless the friend who suggested replacing the solenoid is a mechanic and he has checked out the mower really well, don't automatically assume your solenoid is bad.

The quickest way to start spending money on unneeded parts is to replace items you think are bad. Before you replace a part be sure that is the part causing your problem. Otherwise you are setting yourself up for a frustrating game of hide and seek.


Can a bad solenoid prevent a lawn mower from starting? Whenever my son gets on the mower to cut the grass and he turns the key nothing happens. Maybe there will be a click sometimes. He has learned that if he tries to start it several times and then leaves and comes back the mower will usually start.

The problem is we never know how log starting the mower will take. It could be five minutes or as many as 20 minutes. At some point, I'm guessing the mower is not going to start at all. A friend told us the mower might need to have the solenoid replaced because the battery and the spark plugs are good.

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