iRobot Roomba F21 Error Code Fix (Vacuuming/Evacuation Fault)

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What This Error Means

F21 on a Roomba means a vacuuming/evacuation fault.

Translated: the robot’s suction system or the Clean Base can’t move air right — usually a clog, a soaked or filthy filter/bin, a full or mis-seated bag, or a failing vacuum motor.

Official Fix

Do what iRobot support expects you to try first. Go in this order.

  • 1. Get the robot off the base
    • Pick Roomba up and set it on the floor.
    • Unplug the Clean Base from the wall for 60 seconds. Leave it for now.
  • 2. Empty and reset the dust bin
    • Press the bin release and slide the bin out.
    • Dump everything out of it.
    • Look inside the bin’s air path (the hole where the suction comes in and where it evacuates to the base). Pull out hair, dust wads, and chunks.
    • If you ever rinsed the bin: make sure it is bone dry. If it feels even slightly damp, leave it out 24 hours to dry.
  • 3. Deal with the filter properly
    • Remove the filter from the bin.
    • Do not wash the filter. If you did, that’s a big reason for F21. Wet filter = blocked airflow.
    • Take it outside and bang it gently on a trash can to knock out dust.
    • If it’s caked solid, torn, or smells musty-wet, stop wasting time. Replace it.
  • 4. Check the robot’s suction path
    • Flip Roomba over.
    • Pop out the brushes/rollers. Clean hair and string off the ends and from the brush housing.
    • Look into the suction opening behind the brushes. If you see packed dust, use your fingers, a chopstick, or a small brush to pull it out.
    • Spin the side brush by hand. If it’s jammed with hair, clean or replace it. A jammed side brush can feed clogs.
  • 5. Clean Base checks (if you have a self-empty dock)
    • Open the Clean Base bag door.
    • Make sure the bag collar is fully pushed down on the nozzle. If it’s not seated, the base can’t pull air and you’ll get F-codes.
    • If the bag feels heavy or obviously full, replace it.
    • Look into the round or rectangular suction port where the Roomba docks. Clear any visible dust mats, chunks, pet hair, or Lego bits.
    • Check the floor right in front of the base for anything tall the robot might be ramming into while trying to evacuate.
  • 6. Reassemble and power-cycle
    • Reinstall the (dry) filter into the bin.
    • Slide the bin back into the robot until it clicks.
    • Plug the Clean Base back into the wall and wait 30 seconds.
    • Dock the Roomba on the base.
    • In the app or on the robot, start a quick cleaning run and let it try one evacuation cycle.
  • 7. If F21 pops again immediately
    • Try a full reboot of the robot (check your model, but most i/j/s: press and hold CLEAN until you hear a tone, then release).
    • Make sure the app firmware is up to date.
    • If F21 still returns after a cleanout and reboot, official line is: contact iRobot support for possible vacuum motor / Clean Base service.

The Technician’s Trick

When the official steps don’t clear F21 but the robot still runs, here’s what techs actually do on out-of-warranty units.

  • 1. Deep-clear the hidden clog
    • Pull the bin out.
    • Take a strong household vacuum with a narrow nozzle.
    • Vacuum directly over the robot’s bin opening for 30–60 seconds. You’re trying to suck out crap from the internal duct that you can’t see.
    • On the Clean Base, do the same from the front suction port and, if there’s a rear service opening, from the back too.
  • 2. Reset the evacuation system
    • Unplug the Clean Base.
    • Hold CLEAN on the robot for ~20 seconds until it plays the reset tone.
    • Plug the base back in, dock the robot, and let it sit for a couple of minutes before starting a test run.
  • 3. Last-ditch: open it (only if you’re handy and out of warranty)
    • Remove the bottom plate of the Roomba (small Phillips screws).
    • Locate the suction channel behind the brush module. You’ll often find a compacted dust brick where the duct bends.
    • Pick it out carefully, then vacuum the area.
    • If you power it up and the fan doesn’t spin or squeals, the vacuum motor is probably shot. At that point, you’re into parts replacement or a new robot.

Is It Worth Fixing? (The Financial Verdict)

  • ✅ Fix: Robot under ~4–5 years old, first time seeing F21, runs fine otherwise. A new filter, bag, and a thorough clean are cheap and usually solve it.
  • ⚠️ Debatable: Repeated F21 on an older Roomba or Clean Base where you may need a new bin or vacuum motor but the battery and brushes are still decent.
  • ❌ Replace: F21 plus weak cleaning, noisy or dead fan, worn battery, and other issues. Motor + battery + labor can get close to the cost of a newer robot with warranty.

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