Robot Mower Blades Not Spinning or Not Cutting? Fixes

On this page4 sections

1. Why this happens
2. Fix it in order
3. If it still will not cut, look at settings and conditions
4. When it is the robot, not your lawn

What is going wrong

• 1Packed clippingsWet grass compacts under the deck into a mat that binds the disc, and it is the commonest cause by a wide margin.
• 2The bladesRazor blades pivot on the disc. One jammed against the housing stops the whole assembly.

Why this happens

A robot mower cuts with small blades that pivot on a spinning disc under the deck. That disc sits close to the ground and gathers wet clippings, matted grass, and yard debris every time it runs. When enough material builds up, it wraps the disc and binds the shaft, so the motor either stalls or spins but cannot reach the grass. Dull or worn pivoting blades, a cutting height set higher than the grass, and a cutting motor that has failed produce the same visible result, which is a machine that drives normally but leaves the lawn uncut.

Fix it in order

Work through these from the top. Power the mower off and lift it so the underside faces you before you touch the deck.

1. 1

   Disc cleared

   Clear the blade disc.

   Pull away any grass wound around the center of the disc and the blade pivots. Wound material is the single most frequent reason the disc will not turn.

2. 2

   Deck scraped

   Clean under the deck.

   Remove caked clippings, mud, and debris from the whole underside. A buildup here drags on the disc and blocks the blades from swinging out to cut.

3. 3

   Blades checked

   Check the blades themselves.

   Confirm the small blades swing freely on their pivots and are not cracked, bent, or worn to a rounded edge. Worn blades tear rather than cut. Replace the full set when they are dull, and follow the blade type and torque in your manual.

4. 4

   Height lowered

   Lower the cutting height.

   If the height is set above the current grass length, the blades never reach it. Drop the setting a step and run a short test.

5. 5

   Spun by hand

   Test the disc by hand.

   With the machine off, spin the disc. Smooth free rotation points to a settings or blade issue. Grinding, stiffness, or play in the shaft points to the motor or a bearing.

6. 6

   Supervised start

   Watch a supervised start.

   Place it on grass and start a cycle where you can see the disc. If the drive wheels move but the disc stays still after cleaning, the fault is in the cutting motor or its controller.

If it still will not cut, look at settings and conditions

• Wet grass. Damp clippings clump and re-coat the disc within minutes. Mow when the lawn is dry.
• Height mismatch after growth. A schedule that skipped days can leave grass taller than the deck can manage in one pass. Cut more often, or lower the height temporarily.
• Safety lift or tilt sensors. Many models stop the blades if they read a lift or steep tilt. Debris on those sensors can hold the blades off. Check the manual for their location and clean them.
• Blade fasteners. Confirm each blade and its screw or clip is present and tight. A missing fastener can unbalance the disc and trip a fault.