When you are having trouble getting your mower blades to spin, you’ll need to look for items that can keep power from getting to the clutch and items on the mower deck that may fail to allow the blades to rotate.
Simplicity mower blades won’t engage or turn on when the battery is weak; the PTO switch or safety switch is faulty; the clutch is bad; or the deck belt, pulley, tensioner bracket, or tensioner spring is worn.
Remove the spark plug boots and ignition key prior to performing repairs. Wait for all of the parts to stop moving. Consult your operator’s manual for more safety precautions you need to follow for safety.
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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
Things to check when your mower blades won’t work:
- Weak or bad battery
- Faulty PTO switch
- Bad safety switch
- Blown fuse
- Worn clutch lever, cable, or engagement linkage (manual clutch)
- Bad clutch
- Worn deck belt
- Worn idler tension bracket and spring
- Bad pulley
Simplicity Mower Blades Won’t Turn On or Engage
If your mower uses an electric clutch, you’ll need to make sure you are getting power to the clutch. This includes checking the battery, safety switch, PTO switch, and fuse.
On a manual engagement clutch, you’ll need to check the clutch cable, lever, linkages, and bushings.
Weak Battery
An electric clutch uses power from the battery. When the battery is weak, it is unable to provide sufficient power to the clutch solenoid to engage the mower blades.
Check the voltage of the battery using a multimeter. A fully charged 12-volt battery should give you a reading of about 12.7 volts.
Charge the battery when you get a reading less than this. If your battery continues to die you can find common things that are causing this in 5 Things That Are Draining the Life of Your Lawn Mower Battery.
Charge a Battery: Use a battery charger to charge a battery. Before you continue, wear protective gear to protect your skin from electrical shock and protect your eyes. Follow these steps to charge your riding mower or zero-turn battery with a charger:
- Access the battery and terminals. You may need to use a screwdriver to uncover the battery. You will find the battery under the hood or under the seat. Do not remove the battery from the casing.
- Connect the battery charger cables beginning with the positive cable first. This is the red cable or the one with the plus sign. Place the cable on the positive battery terminal.
- Attach the negative cable to the negative battery terminal. This is the black cable or the one with the negative sign.
- Do not touch anything that doesn’t have a rubber coating to prevent electrocution.
- Set the charger’s voltage and amperage level to the desired level. The average volt level for lawn mower batteries is usually 12 volts. More amperage charges the battery faster. Start with two amps and work up to no more than 10 amps. A slow charge is best.
If you find the battery won’t hold a charge, you must replace it with a new one. You can find 12-volt lawn mower batteries at your local hardware or automotive store. You may also find batteries at your local Simplicity mower dealership.
Bring the old battery with you. Most places will charge you a core fee unless you provide them with your old battery. You can expect the core fee to be around $20 if you don’t return the old battery.
Faulty PTO Switch
The PTO switch is usually a knob installed on a mower that allows voltage from the battery to power the clutch. When the switch fails, the blades won’t turn on.
Check for continuity in the switch. Replace a switch with a break in continuity.
Bad Safety Switch
A Simplicity uses a safety switch in the seat as part of its operator presence system. The seat switch is installed under the seat and is engaged when the operator is in the seat.
As part of the safety system, the lawn mower blades won’t turn on without the operator in the seat. If you do get the blades running, they will shut off if you leave the seat with the blades engaged.
If the seat switch fails to work, it may not properly sense the operator. The safety system will prevent the blades from engaging when there is a bad seat switch.
Test the seat switch using a multimeter or you can temporarily bypass the safety switch to identify a bad switch. Do not operate a mower without the safety switch installed for your safety.
Always have safety switches installed and working on your equipment.
Blown Fuse
When you aren’t getting power from the battery to the clutch, you may have blown a fuse. The fuse is used to protect the electrical system.
Replace a blown fuse with the same amperage fuse. If you continue to blow fuses, I recommend taking your mower to a Simplicity service dealership or a lawn mower repair shop to find the root cause of the electrical failure.
Worn Clutch Cable, Lever & Linkages on a Mower with a Manual Clutch
You will find a clutch lever and cable on a mower with a manual engagement clutch.
Check the condition of the clutch lever, cable, spring, bushings, and linkages to make sure the clutch is being engaged and the parts are not worn
Replace any worn parts.
Bad Clutch
The PTO (Power Take Off) clutch transfers power from the engine to the blades by engaging the drive belt. A clutch that is worn or faulty must be replaced when it fails to power the blades.
For more details on clutches, check out A Look into How Lawn Mower Clutches Work.
Worn Deck Belt
When the mower blades won’t turn, check the mower deck belt. Over time the belt can wear and fail to turn the mower blades.
A worn or bad Simplicity deck belt is one that has cracks, wear, fraying, or a shiny glazed appearance. A worn deck belt may also sit deep in the pulley grooves.
Replace a worn belt. Even if the belt isn’t the main reason why your blades won’t engage, you must replace it when it begins to show signs of wearing.
The belt gripping the pulleys affects blade speed. A fast blade speed is required to create suction under the deck to lift the grass and give it a nice even cut.
Worn Idler Tensioner Arm & Spring
You will find a tensioner arm and spring used to hold the idler pulleys inline. On most mower decks, the pulley will be on one side of the bracket and the spring will be on the other side.
The hole in the bracket where the spring is attached can become worn or the spring itself can become worn. This can cause the belt to become loose, vibrate and come off the pulleys.
Worn Bearing in a Pulley
You will find a bearing in each pulley. The bearing can wear so the pulley no longer sits parallel to the mower deck. The worn bearing will allow movement in the pulley so it wobbles.
One side of the pulley may be sitting higher off the deck than the other side. The extra movement in the pulley can cause the deck belt to roll off of the pulley.
Replace a pulley where the bearing is found to be bad.