the main brush doesn't spin at all during cleaning, just drags on the floor.

Diagnosis

The Roborock Q7 Max Plus utilizes a high-torque DC motor to drive the all-rubber dual-brush system. When the brush fails to spin and simply drags, it is typically caused by a "mechanical seizure." This happens when long hair, carpet fibers, or pet fur migrate past the brush seals and wrap tightly around the end caps of the brush roll. As these fibers compress, they create enough friction to lock the axle, triggering the robot's internal over-current protection, which cuts power to the motor to prevent it from burning out. Alternatively, the issue may be a failure of the square drive coupling. The Q7 Max Plus uses a plastic drive gear that interfaces with the brush's square mounting head. If a foreign object (like a coin or small pebble) gets lodged in the brush housing, it can shear the teeth off this gear or strip the motor shaft. You can confirm this by attempting to spin the brush by hand while it is installed; if it spins freely but the robot reports a "Main Brush Stuck" error or the motor makes a humming sound without movement, the drive gear is likely stripped.

How to Fix It

Follow these precise steps to clear the obstruction and restore drive functionality:

1. Power down the robot using the physical power switch on the side or via the Roborock app to prevent accidental motor engagement during cleaning.
2. Flip the unit over and locate the two release tabs on the main brush cover. Press these tabs and lift the cover away from the chassis.
3. Lift the rubber brush roll out of the housing. Note that the Q7 Max Plus uses a dual-roller system; remove both rollers if applicable.
4. Remove the plastic end caps from both sides of the brush roll. These are the primary collection points for hair. Use a pair of precision tweezers or a seam ripper to cut through the hair rings wrapped around the axle.
5. Inspect the brush housing's interior. Reach into the left and right sockets and ensure no debris is preventing the brush from seating deeply.
6. Locate the square drive gear (the motor output shaft) on the left side of the compartment. Use a flashlight to check for missing teeth or a rounded-off square edge.
7. Clean the contact points of the drive gear with a dry microfiber cloth to remove any dust buildup.
8. Reinsert the brush roll, ensuring the square end of the brush fits snugly and fully into the drive gear. You should feel a distinct "click" or a firm seat.
9. Replace the cover and run a "Spot Cleaning" cycle to verify the rollers are spinning.

If That Didn't Work

• Replace the Brush Roll Assembly: If the internal plastic ribs of the brush roll have warped or the square drive head is stripped, the motor will spin but the brush won't. Replace the roll with a genuine Roborock Q7 Max replacement part (Part No: Q7-BRUSH-KIT).
• Check for Motor Failure: If the brush is clean and the gear is intact but you hear no motor noise during the start-up sequence, the DC motor may have failed. This requires opening the chassis to test the motor leads with a multimeter for continuity.
• Inspect the Mainboard Fuse: In rare cases, a severe jam can blow a surface-mount fuse on the main PCB. If other functions (like the side brush) work but the main brush is completely dead, the motherboard may need a professional repair or replacement.
• Reset the Firmware: Occasionally, a software glitch can cause the robot to "think" the brush is jammed when it isn't. Perform a hard reset by holding the Home and Spot clean buttons simultaneously until the voice prompt confirms the reset.

Heads Up

• Avoid Wet Debris: Never use the Q7 Max Plus on damp floors. Moisture can migrate into the brush motor housing, causing corrosion on the drive gear and leading to premature motor failure.
• Weekly Maintenance: To prevent drive gear stripping, remove the brush rolls once a week and clear the end caps. Hair buildup creates "drag" that puts excessive stress on the motor.
• Check the Seals: Ensure the rubber gaskets around the brush housing are seated correctly. If they are pinched or torn, more hair will enter the motor compartment, leading to more frequent jams.