If your mower engine runs but the blades will not engage, inspect the drive system and safety controls before ordering parts.
Common causes
- Broken, loose or incorrectly routed deck belt
- Worn belt tensioner or idler pulley
- Damaged spindle or seized spindle bearing
- Electric PTO clutch, switch, fuse or wiring fault on equipped models
- Mechanical PTO linkage problem on manual-engagement models
- Operator-presence or safety-interlock condition
Start with the deck belt
With the engine off, key removed and spark plug disconnected, inspect the deck belt for breakage, glazing, severe cracking or a belt that has jumped off a pulley. Compare routing with the decal or manufacturer diagram for your exact mower and deck.
Inspect pulleys and spindles
Check idler pulleys and spindle pulleys for obvious damage, looseness or binding. A failing spindle bearing can prevent normal blade operation and can damage belts.
Electric PTO systems
If the belt and deck hardware appear normal, an electric PTO system may require electrical diagnosis. Do not bypass safety switches. Use the manufacturer wiring/service information for your exact model.