Even quality coffee grinders encounter problems over time. The good news is that many common issues have simple solutions you can implement at home without professional repair. This guide covers the most frequent grinder problems, their causes, and step-by-step fixes.
Knowing how to troubleshoot your grinder saves money on repairs and ensures you're always able to enjoy freshly ground coffee.
Inconsistent Grind Size
Inconsistent grounds—a mix of fine powder and larger chunks—is one of the most common complaints. This directly affects coffee taste, causing uneven extraction.
Possible Causes and Solutions
Worn burrs: Over time, burrs lose their sharpness. Steel burrs typically last 500-800 kg of coffee. Signs of wear include visible dullness, rounded edges, and progressive inconsistency despite cleaning.
Solution: Replace the burrs. Most manufacturers sell replacement burr sets. This is usually a straightforward DIY job.
Misaligned burrs: After cleaning or burr replacement, burrs may not be properly seated, causing uneven grinding.
Solution: Disassemble and reassemble the burrs carefully, ensuring proper alignment with any markers or notches.
Coffee buildup: Old grounds packed between burrs or in the chute affect particle flow.
Solution: Deep clean the grinder, removing burrs if possible and brushing thoroughly.
Using the wrong grinder: Blade grinders inherently produce inconsistent grinds; this isn't fixable—it's the technology's limitation.
Solution: Upgrade to a burr grinder for consistent results.
Quick Test for Consistency
Grind a dose and spread it on a white surface. Look for uniformity. Some variation is normal, but you shouldn't see obvious powder mixed with large fragments.
Excessive Static
Static electricity causes grounds to cling to the grinder, portafilter, grounds bin, and everything nearby. It's messy and can affect dosing accuracy.
Possible Causes and Solutions
Low humidity: Dry air increases static. This is common in air-conditioned environments or during dry seasons.
Solution: The Ross Droplet Technique (RDT)—add a single drop of water to beans before grinding. This dramatically reduces static without affecting the grind.
Fresh-roasted beans: Very fresh beans (within days of roasting) can produce more static.
Solution: Allow beans to degas for a few days after roasting, or use RDT.
Plastic components: Grinders with plastic hoppers, chutes, or grounds bins generate more static than metal ones.
Solution: Replace plastic grounds bins with metal alternatives if available, or use RDT.
Grind setting: Finer grinds tend to produce more static.
Solution: Use RDT, or accept some static as normal for espresso-fine grinding.
Grinder Running Slowly or Struggling
When your grinder seems to work harder than usual or takes longer to grind the same amount of coffee, something is impeding operation.
Possible Causes and Solutions
Coffee buildup: Accumulated grounds create friction and resistance.
Solution: Deep clean, including burr removal and thorough brushing.
Overfilled hopper: Too many beans pressing down can slow the motor.
Solution: Fill hopper only to recommended levels.
Very fresh or oily beans: Fresh beans are denser; dark roasts have surface oils. Both can slow grinding.
Solution: This is normal variation. Dark oily roasts may require more frequent cleaning.
Motor issues: For electric grinders, a struggling motor may indicate electrical problems or wear.
Solution: If cleaning doesn't help, consult a professional or contact the manufacturer.
For manual grinders: Difficulty turning may indicate burr contact (too fine) or debris in the mechanism.
Solution: Adjust coarser, clean thoroughly, and check for foreign objects.
Grinder Won't Turn On
An electric grinder that won't start is frustrating, but often the fix is simple.
Possible Causes and Solutions
Safety interlock not engaged: Many grinders have safety switches that prevent operation when the hopper or grounds bin isn't properly seated.
Solution: Remove and reseat the hopper and grounds bin, ensuring they click into place.
Power issues: The outlet may be the problem, not the grinder.
Solution: Test the outlet with another device; try the grinder in a different outlet.
Thermal protection activated: After extended use, some grinders shut down to prevent overheating.
Solution: Wait 10-15 minutes for the grinder to cool, then try again.
Jammed burrs: A foreign object (like a small stone that occasionally hides in coffee beans) can jam the burrs.
Solution: Disconnect power, remove the hopper, and check for obstructions. Remove any foreign objects.
Safety First
Always unplug electric grinders before inspecting burrs or internal components. Never put fingers near burrs while the grinder is connected to power.
Strange Noises
Unusual sounds often indicate something amiss. Learning to identify these sounds helps diagnose problems.
Possible Causes and Solutions
Squealing or high-pitched noise: Often indicates metal-on-metal contact, possibly from misaligned or worn burrs.
Solution: Check burr alignment; worn burrs may need replacement.
Rattling: Loose components vibrating during operation.
Solution: Check that all parts are properly secured—hopper, grounds bin, burr carrier.
Grinding/clicking at coarse settings: Some grinders make this sound when burrs are far apart—it's often normal.
Solution: If the sound is new, check for debris or misalignment.
Motor whining: This may indicate bearing wear or motor strain.
Solution: If accompanied by slow operation, professional service may be needed.
Grounds Escaping or Leaking
Coffee grounds appearing outside the grounds bin indicates seal or alignment issues.
Possible Causes and Solutions
Overfilled grounds bin: The bin is full and grounds are backing up.
Solution: Empty the bin more frequently; don't let it overflow.
Poor seal: Worn gaskets or warped components can create gaps.
Solution: Inspect seals and gaskets; replace if worn.
Misaligned chute: If components aren't properly seated, grounds can escape.
Solution: Disassemble and reassemble, ensuring proper alignment.
Coffee Tastes Bad Despite Fresh Grinding
When properly ground fresh coffee still tastes off, the grinder itself may be contributing unwanted flavours.
Possible Causes and Solutions
Rancid oil buildup: Coffee oils oxidise and become rancid, tainting fresh grounds.
Solution: Deep clean, including burr removal. Consider using grinder cleaning tablets.
Old retained grounds: Stale grounds stuck in the grinder mix with fresh coffee.
Solution: Purge with a few beans before grinding your dose; clean regularly.
Cross-contamination: If you've ground spices or flavoured coffee, residues may remain.
Solution: Deep clean; grinding plain rice can help absorb residual flavours (though some manufacturers advise against rice).
Prevention: Maintenance Routine
Many problems are preventable with regular maintenance:
- Daily: Empty grounds bin; quick brush of visible areas
- Weekly: Brush burrs and chute; wipe hopper
- Monthly: Deep clean with burr removal
- Every few months: Consider cleaning tablets
- Annually: Inspect burrs for wear
When to Seek Professional Help
Some issues require professional repair:
- Motor replacement
- Electronic control failures
- Warranty repairs
- Problems you can't diagnose
Contact the manufacturer first—many offer excellent support and repair services. For premium grinders, authorised service is worth the cost to protect your investment.
Key Takeaway
Most grinder problems stem from lack of cleaning or normal wear. Regular maintenance prevents many issues, and simple troubleshooting can fix most problems at home.