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8 Reasons Cub Cadet Mower Blades Won’t Engage or Turn On

You have a riding mower or a zero-turn mower and your blades won’t turn on. What good is a mower when you can’t get the blades to engage?

Cub Cadet mower blades won’t engage or turn on when the deck belt is worn; the tensioner arm or spring is worn; a pulley is bad; the PTO switch is faulty; the clutch is bad; the battery is weak, or the fuse is blown.

Always follow the safety precautions found in the Cub Cadet operator’s manual before performing any repairs. Always remove the ignition key and spark plug wires.

Mower deck blades won't engage

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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.

Cub Cadet Mower Blades Won’t Engage or Turn On

Worn Deck Belt

When the mower deck belt is worn, it can slip on the pulleys and fail to turn the mower blades. Inspect the belt and check for visible signs of wearing including cracks, wearing, fraying, or a shiny appearance.

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.

Check out Why Your Cub Cadet Belt Keeps Coming Off or Breaking for additional items that cause this to happen.

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 Pully Bearing

A Cub Cadet 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.

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.

Worn Clutch Cable on a Manual Clutch Mower

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.

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 Cub Cadet 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 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 Cub Cadet 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 Cub Cadet’s electrical system.

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

Still Having Problems with Your Cub Cadet Mower?

If these tips haven’t solved your problem or if you are experiencing a different problem with your mower, check out my guide showing the most common issues and solutions: Common Cub Cadet Problems.

Here you’ll find the causes of issues like the mower not starting, a bad cut, a vibration, or a smoking problem. I include solutions along with links to more in-depth information.