Fix John Deere Lawn Mower
Nothing runs like a Deere - until it doesn’t. Most John Deere mower problems are the same stuff that kills any mower: old gas, dead batteries, worn belts. The green paint doesn’t make it immune. Here’s how to diagnose and fix the common issues.
Table of Contents
- Won’t Start Problems
- Belt Problems
- Blade Issues
- Transmission Problems
- Electrical Issues
- When to Call a Pro
Won’t Start Problems
Quick Diagnosis
Riding mowers:
- Turn key - does it click?
- Check battery voltage (12.6V fully charged)
- Verify safety switches engaged
- Check fuel freshness
Push mowers:
- Pull cord - does engine turn?
- Check spark plug
- Verify fuel in tank
- Test primer function
[NEED IMAGE: John Deere won’t start diagnostic flowchart]
Battery Issues (Riding Mowers)
Symptoms:
- Click but no crank
- Slow cranking
- Nothing happens
Fix:
- Test battery voltage
- Clean terminals
- Charge or replace battery
- Check charging system
Battery specs: 12V, typically 230-300 CCA
Fuel System Problems
Symptoms:
- Cranks but won’t fire
- Starts then dies
- Runs rough
Fix:
- Drain old fuel
- Replace fuel filter
- Clean carburetor
- Check fuel pump (if equipped)
Safety Switch Issues
John Deere mowers have multiple safety switches:
- Seat switch
- Brake/clutch switch
- PTO switch
- Reverse switch
Diagnosis: Each switch can be bypassed temporarily for testing. Never leave bypassed for operation.
Belt Problems
Deck Belt Issues
Symptoms:
- Blades won’t engage
- Squealing when PTO engaged
- Belt keeps coming off
- Blades slow down under load
Common causes:
- Worn belt (cracks, glazing)
- Bad idler pulley
- Bent spindle
- Debris in pulley grooves
[NEED IMAGE: John Deere deck belt inspection]
Belt Replacement
Tools needed:
- Socket set
- Flathead screwdriver
- New belt
Steps:
- Disconnect spark plug or battery
- Lower deck to lowest position
- Remove belt guards
- Release tensioner
- Note belt routing (take photo)
- Remove old belt
- Route new belt per diagram
- Release tensioner
- Verify proper seating
- Test operation
Drive Belt Issues
Symptoms:
- Won’t move forward/reverse
- Sluggish response
- Squealing when moving
Fix: Same process as deck belt but requires more disassembly on most models.
Blade Issues
Dull Blades
Symptoms:
- Ragged cut edges
- Brown grass tips
- Takes longer to mow
Fix:
- Remove blades
- Sharpen with file or grinder
- Balance before reinstalling
- Torque to 35-50 ft-lbs
Bent Blades
Symptoms:
- Vibration while mowing
- Uneven cut height
- Unusual noise
Fix: Replace blade. Don’t try to straighten.
Spindle Problems
Symptoms:
- Blade wobbles
- Grinding noise
- Smoke from deck area
Fix:
- Check spindle bearing play
- Replace bearing or complete spindle
- Verify pulley alignment
Transmission Problems
CVT Issues (100 Series)
Symptoms:
- Loss of speed
- Jerky movement
- Grinding noise
Common causes:
- Worn CVT belt
- Damaged variable pulley
- Low transmission fluid (some models)
Hydrostatic Issues (S200 Series)
Symptoms:
- Won’t move
- Weak movement
- Whining noise
Fixes:
- Check transmission oil level
- Replace transmission filter
- Purge air from system
- Check drive belt condition
[NEED IMAGE: John Deere transmission troubleshooting]
Transmission Fluid
| Model Type | Fluid | Capacity |
|---|---|---|
| 100 Series CVT | N/A | Sealed |
| S200 Hydro | TY22035 | Check manual |
Electrical Issues
Battery Not Charging
Check order:
- Battery condition
- Belt driving alternator
- Alternator output
- Voltage regulator
- Wiring connections
Lights/Accessories Not Working
Check order:
- Fuse condition
- Bulb condition
- Switch operation
- Ground connections
PTO Won’t Engage
Check order:
- PTO switch
- Seat safety switch
- PTO clutch
- Wiring connections
When to Call a Pro
DIY-Friendly Repairs
- Belt replacement
- Blade sharpening/replacement
- Filter changes
- Battery replacement
- Basic electrical troubleshooting
Professional Repairs
- Transmission rebuild/replacement
- Engine internal repairs
- Hydrostatic system work
- Electrical system diagnosis
- Major frame damage
Repair Cost Estimates
| Repair | DIY Cost | Shop Cost |
|---|---|---|
| Belt replacement | $25-50 | $100-150 |
| Blade replacement | $40-80 | $75-125 |
| Carburetor clean | $15-30 | $75-150 |
| Transmission | $200-400 | $400-800 |
| Engine rebuild | $300-600 | $800-1500 |
Maintenance to Prevent Problems
Every 25 Hours
- Check oil level
- Clean air filter
- Inspect belts
- Check tire pressure
Every 50 Hours
- Change engine oil
- Replace oil filter
- Sharpen blades
- Check battery
Every 100 Hours
- Replace spark plug
- Replace air filter
- Replace fuel filter
- Service transmission (if applicable)
Related Guides
- John Deere Lawn Mower Parts Diagram
- Lawn Mower Won’t Start
- Riding Mower Belt Replacement
- How to Sharpen Mower Blades
Summary
Most John Deere lawn mower problems are DIY-fixable. Start with the basics: fresh fuel, good spark, clean air. Belt and blade issues are common but straightforward. Know your limits - transmission and major engine work often needs professional attention.