You pull the PTO switch to engage the mower blades but nothing happens. You can’t get your blades to spin. I’ll go through the most likely reasons for the problem so you can repair it and get back to mowing.
Gravely lawn mower blades won’t engage or turn due to a worn or stretched mower deck belt; a belt that has come off the pulleys; a bad PTO switch; a faulty clutch; a weak battery; a bad safety switch or a bad fuse.
Never reach under the mower deck until you have followed all safety precautions listed in the Gravely operator’s manual. This includes removing the ignition key, removing the spark plug wire(s), and waiting for all parts to stop moving.
This post may include affiliate links. Purchases made through these links may provide a commission for us, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.
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.
Gravely Mower Blades Won’t Turn On or Engage
1. Worn Deck Belt
Check the mower deck belt when the blades on your mower no longer turn or turn slowly. The deck belt is used to turn the pulleys so the blades rotate under the deck.
When the belt becomes worn, it no longer grips the pulleys and begins to slip. The blades won’t turn or may turn slowly.
Look at the belt and inspect it for signs of wear including cracks, fraying, or a shiny glazed appearance. Check to see if the belt is sitting deep in the pulleys. This is also a sign of wear.
Replace a worn Gravely deck 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.
2. Belt Came Off the Pulleys
If the belt has fallen off the pulleys, it will no longer turn them to move the mower blades. In addition to a worn belt, look for a stretched belt, bad pulley, worn tensioner arm, or missing spring.
You can find a list of additional items that will cause the Gravely 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 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 and vibrate off the pulleys.
Worn Pulley Bearing
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.
3. 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.
4. 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.
5. 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 Gravely 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 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.
6. Bad Safety Switch
A Gravely 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.
7. 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 Gravely electrical system.
Replace a blown fuse with the same amperage fuse. If you continue to blow fuses, I recommend taking your mower to a Gravely service dealership or a lawn mower repair shop to find the root cause of the electrical failure.
Still Experiencing Problems with Your Gravely Lawn Mower?
Own a lawn mower long enough, you’ll start running into problems with it starting, not continuing to run, smoking, leaking gas, giving a bad cut, vibrating, or another issue.
To help you save time and money, I have put together a guide to help you troubleshoot the next problem that develops on your Gravely mower.
You can find this guide at Common Gravely Lawn Mower Problems & Solutions.
If you are unsure how to perform diagnostics and repairs on your Gravely lawn mower safely, 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 Gravely lawn mower dealership or lawn mower repair shop will be able to help you solve your problem.