You move your zero-turn to the lawn to mow it. When you go to engage the blades with the PTO switch, the blades won’t turn on. When this happens, you’ll need to check the components that power the clutch in addition to component failures on the deck.
The mower blades on a zero-turn lawn mower won’t engage or turn on due to a worn deck drive belt, a worn idler tensioner, stretched or missing tensioner spring, a bad pulley bearing, a faulty PTO switch, a bad clutch, a weak battery, a bad safety switch, or a blown fuse.
Never reach under the mower deck until all safety precautions have been met. Read the operator’s manual and follow all safety instructions.
This includes removing the ignition key and spark plug wires. Wait for all parts to stop moving.
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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.
Zero Turn Mower Blades Won’t Turn On or Engage
Worn Deck Belt
The deck drive belt rotates on the idler pulleys to turn them so the blades rotate. When the belt is worn, it may fail to grip the pulleys and turn them.
This can cause the blades to fail to turn or they may turn very slowly and not cut the grass.
Inspect the deck belt to check its condition. Look for visible signs of wearing including cracks, fraying, and a glazed appearance.
A worn belt may also sit deep in the pulley grooves.
Replace the belt if it is worn. 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.
Belt Came Off the Pulleys
The belt may have come off the pulleys causing your mower to fail to turn the mower blades. I have listed a couple of common causes for this here.
If this is your problem, check out this article for additional reasons that can cause a zero-turn belt to come off.
Worn Idler Tensioner Arm & Spring
You will find a tensioner arm and spring that holds the idler pulley in line. The bracket typically has a pulley on one side and a spring 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 and vibrate off the pulleys.
Worn Pulley Bearing
A belt that is coming off your mower can be the result of bad bearings in your pulleys. Bearing failure can cause a pulley to move so it no longer sits flat and parallel to the deck.
One side of the pulley should not be sitting higher off the deck than the other. The belt can roll off a pulley that isn’t running flat. Replace a pulley where the bearing is found to be bad.
Faulty PTO Switch
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.
Use a multimeter to check for continuity in the switch. Replace a switch with a break in continuity.
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.
Weak Battery
A zero-turn 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 mower’s 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 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
A zero-turn uses a safety switch in the seat as part of its operator presence system. The seat switch is installed under the seat to sense when the mower 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 the seat switch fails to work, it may not properly sense the operator. The safety system will prevent the blades from engaging with 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 a blown fuse. The fuse is used to protect the zero-turn’s electrical system.
Replace a blown fuse with the same size fuse. If you continue to blow fuses, I recommend taking your mower to your local lawn mower dealership or a lawn mower repair shop to find the root cause of the electrical failure.
Still Experience Problems with Your Zero Turn Mower?
Many different types of problems can develop in a mower. It doesn’t matter what brand you own.
While some mowers are built with stronger materials, bigger filters, better engines, and tougher spindle housings, they are all going to break down and cause issues at some time. Some may just not develop problems as quickly as others.
I put together a guide with common things that go wrong on zero-turns. In this guide, you will find a list of causes and solutions for a mower dying, smoking, vibrating, not starting, having cutting issues, and more.
Check out my guide at Common Zero Turn Mower Problems: How to Fix Them
If you still can’t find the solution to your problem or you don’t feel comfortable troubleshooting or repairing your mower, it is best to have an experienced mechanic check out your mower.
You can visit your local dealership that provides repair support for your brand mower. You may also find a lawn mower repair shop with experienced small engine mechanics.