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Spartan Mower Blades Won’t Engage or Turn On: SOLVED!

You pull up the PTO switch to turn on the blades, but nothing happens. The blades won’t engage.

Spartan lawn mower blades won’t engage or turn on due to a worn or stretched mower deck belt; a worn tensioner bracket or bad pulley causing the belt to fall off; a bad PTO switch; a faulty clutch; a weak battery; a bad safety switch, or a blown fuse.

Never reach under the mower deck until you have followed all safety precautions listed in the Spartan operator’s manual. This includes removing the ignition key, removing the spark plug wires, and waiting for all parts to stop moving.

Spartan zero turn 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.

Spartan Mower Blades Won’t Turn On or Engage

Worn Deck Belt

A worn mower deck belt may not be able to grip the pulleys to turn the mower blades. The belt must be replaced when it is worn.

A worn or bad Spartan deck belt is one that has cracks, fraying or a shiny glazed appearance. A worn deck belt may also sit deep in the pulley grooves.

When the belt slips on the pulleys, it will affect the 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.

Check out Reasons a Spartan Mower Has a Bad or Uneven Cut for more items that can affect your mower’s cut.

Belt Came Off the Pulleys

The pulleys will no longer turn the blades when the belt falls off. Common reasons for a belt coming off the pulleys are a stretched belt, bad pulley, worn tensioner arm, or missing spring.

You can find a list with more items that will cause the Spartan belt to keep falling off the mower deck here.

Worn Idler Tensioner Arm & Spring

You will find a tensioner arm and spring used to hold the idler pulleys inline. On most Spartan mower decks you will find the pulley 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 and vibrate 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.

Faulty PTO Switch

The PTO switch is usually a yellow 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.

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 Spartan 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 Spartan 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 Spartan 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 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 Spartan mower’s electrical system for a surge in power or a short.

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

Still Having Problems With Your Spartan Zero Turn Mower?

It would be nice to own a mower that will never give you problems. However, they don’t exist. When you own a mower long enough, you are bound to run into problems.

The most common of them are problems with starting, smoking, dying, vibrating, and cutting.

I put together a handy guide to help you quickly identify items that can cause a problem with your mower. You can find this guide at Common Spartan Lawn Mower Problems & Solutions.

If you are unsure how to safely perform diagnostics and repairs, it’s best to have a professional complete the repairs.

This will help you avoid personal injury or additional damage to the mower. Your local Spartan lawn mower dealership or lawn mower repair shop will be able to help you solve your problem.