Robot vacuum problems and how to fix them

This hub is deliberately structured against the way troubleshooting content usually works. The standard article opens with a product recommendation and buries the free fix at the bottom, because the free fix earns nothing. We do it the other way round: the cheapest thing that might work goes first, and a replacement part appears only where a worn part is genuinely the cause.

Start here: the ten-minute maintenance pass

Before you diagnose anything specific, do this. It resolves a surprising share of what gets reported as a broken robot, and it costs nothing but a pair of scissors and a dry cloth.

1. Power the robot off. Not docked and idle — off. A brush that starts turning while your fingers are in it is a bad afternoon.
2. Cut the hair off the main brush and the side brush. Most brushes have a cutting groove along the housing. Take the end cap off, pull the brush out and clear both bearings — hair packs into the bearing where you cannot see it and that is what makes the motor labour.
3. Wipe the cliff sensors. They are the small dark windows on the underside. Dust on them is the single most common cause of a robot that reverses away from perfectly flat floor, or refuses to leave the dock.
4. Wipe the charging contacts on the robot and on the dock. A thin film of dust here reads as a failed charge.
5. Clean the filter and check the bin seal. A clogged filter shows up as poor pickup, which people diagnose as a suction fault.
6. Check the wheels turn freely and the caster is not packed with hair. A packed caster makes the robot veer, which the map then tries to correct for, which produces the circling behavior.

The four faults worth their own page

• [It keeps getting stuck](/troubleshooting/keeps-getting-stuck) — usually a physical trap the map cannot represent. The fix is a no-go zone, not a setting.
• [It will not charge](/troubleshooting/wont-charge) — contacts, dock placement and battery age, in that order.
• [It goes in circles](/troubleshooting/going-in-circles) — a wheel, a caster or a sensor, almost never software.
• [Runtime has collapsed](/troubleshooting/battery-life-compared) — what published runtimes mean and when a battery is genuinely done.

What the manufacturers publish about runtime

Stated runtimes are quoted in the quietest mode on the easiest surface, which is why a robot advertised at nearly five hours may manage well under two in practice on carpet at full power. It is not a lie, but it is a laboratory figure and it should be read as one.

Note how few makers publish it at all. Where the cell reads not published, that is what we found on the manufacturer's own page — not a figure we could not be bothered to look up. Doubling back on that: if a figure appears here later it will be because the maker published it, with the date.

Parts, and when a part is actually the answer

Brushes, filters, mop pads and side brushes are consumables and they do wear out. The honest signal is behavioral rather than calendar-based: a filter that no longer looks clean after tapping it out, a brush whose blades have gone soft and rounded, a mop pad that comes out of the wash still stained. Replacing those restores performance. Replacing them because a maintenance reminder fired does not.

The cost-per-year comparison across brands, which is a real difference and one nobody puts in a buying guide, is on replacement parts compared.

When it is not fixable

Two failures are genuinely terminal on most models. A swollen battery — which you will see as a bulging underside or a robot that no longer sits flat — is a safety issue, and the robot should be stopped and the battery disposed of properly rather than run. And a main-brush motor that has been running against a jammed brush for months will eventually go, at which point the repair usually costs more than the machine is worth.

If you are at that point, the useful question is which floor problem sent you here in the first place. Start from the six floor problems rather than buying the same class of machine again.