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9 Reasons Riding Mower Blades Won’t Engage or Turn On

You engage the PTO switch and nothing happens. If it does engage, the mower blades still won’t turn.

Riding mower blades won’t engage or turn on due to a worn deck belt, worn tensioner spring, bad pulley, faulty PTO switch, bad clutch, weak battery, bad safety switch, blown fuse, or worn clutch cable.

Follow the safety precautions outlined in your mower operator’s manual before performing repairs. This includes removing the ignition key and spark plug wires. Wait for the engine to cool and for all parts to stop moving.

Riding mower blades won't engage

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Follow all safety instructions provided in your equipment operator’s manual prior to 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.

Riding Mower Blades Won’t Turn On or Engage

Worn Deck Belt on a Riding Lawn Mower

The deck belt is designed to sit securely around the pulleys to turn the mower blades. When the blade becomes worn, it can fail to sufficiently grip the pulleys.

Inspect the deck belt for wear. This includes visible signs like a stretched belt, cracks developing in the belt, or fraying of the belt. A worn belt may also have a shiny glazed appearance and may sit deep in the pulley grooves.

Replace a worn riding mower deck belt when it is showing signs of wearing. Even if you don’t find the belt being the root cause of the problem, a worn belt will affect blade speed when it slips on the pulleys.

A slow blade speed can result in a bad cut.

Worn Tensioner Spring on a Riding Lawn Mower

You will find a tensioner spring that holds the idler pulleys in line. The hole in the bracket or deck where the spring is attached can become worn or the spring itself can become worn.

This can cause the belt to become loose and vibrate off the pulleys.

Replace a worn or missing tensioner spring. If you find the hole in a bracket is wearing larger, replace the bracket if it is a replaceable part.

Worn Bearing in a Pulley on a Riding Lawn Mower

A worn bearing in a pulley on the deck can cause the deck belt to slip off the pulleys and no longer turn the blades.

This happens when a bad bearing no longer keeps the pulley sitting flat and securely attached to the deck. The pulley may begin to wobble allowing the belt to come off the pulley.

Inspect the deck pulleys. Turn each pulley slowly by hand to make sure they move without restriction. Listen for a bearing noise and feel for a wobbling of the pulley. Each of these is a sign the bear is worn and the pulley must be replaced.

If you find the deck belt keeps falling off or snaps, read Your Belt Keeps Falling Off Your Riding Mower for additional causes.

Faulty PTO Switch on a Riding Lawn Mower

The PTO switch is usually a knob installed on the 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 Clutch on a Riding Lawn Mower

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 Clutch Cable on a Riding Mower with a Manual Clutch

On riding mowers with a manual engagement clutch, you will find a clutch lever and cable. The lever, cable, and linkages can become worn and no longer function.

Check the condition of the clutch lever, cable, spring, bushings, and linkages to make sure the clutch is being engaged. Replace any worn parts you find.

Weak Battery on a Riding Lawn Mower

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 riding 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 Riding Mower 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 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 battery. You can find 12-volt lawn mower batteries at your local hardware or automotive store. You will also find batteries at your local lawn mower dealership.

Bring the old battery with you. Most places will charge you a core fee unless you provide them with your old battery. Core fees average $20.

Bad Safety Switch on a Riding Lawn Mower

As part of the operator presence system, safety switches are used to assist in keeping the user safe. You will find a safety switch located under the seat to indicate to the safety system that the user is in the seat when you sit on it.

The safety system will not allow the blades to turn on without the operator in the seat. If the seat switch fails, the mower blades won’t turn the blades on.

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.

Always have safety switches installed and working on your equipment.

Blown Fuse on a Riding Lawn Mower

When you aren’t getting power from the battery to the clutch, you may have a blown fuse. The fuse is used to protect the mower’s electrical system.

The fuse can blow because of a number of items including a short, bad wiring, or failing components.

Replace a blown fuse with the same capacity fuse. If you continue to blow fuses, I recommend taking your mower to a lawn mower repair shop or your local mower dealership to find the root cause of the electrical failure.

Still Having Problems With Your Riding Mower?

As a lawn mower owner, when you own it long enough, you are going to run into different types of problems. This may include problems where your riding mower is smoking, cutting unevenly, losing power, not starting, leaking fuel, and more.

Check out this handy guide including charts for common riding mower problems and solutions:
Common Riding Lawn Mower Problems & Solutions.

If you are unable to fix your riding mower or don’t want to attempt a more complicated repair, have your local lawn mower dealership or repair shop for assistance.