Prusa Fan Error — Hotend or Print Cooling Fan Stopped

What Does This Error Mean?

Fan Error on Prusa printers means one of the fans on the toolhead has stopped spinning — usually the hotend fan (always on) or the print cooling fan (varies by print).
Clean dust and filament debris off the fan blade with a soft brush.
If the fan still doesn't spin, the bearing has failed and the fan needs replacement.
Prusa sells replacement fans for under 20 EUR each.

Affected Models

Prusa MK3S+
Prusa MK4
Prusa MK4S
Prusa Mini+
Prusa XL

Common Causes

Dust or filament debris jamming the fan blade
Fan bearing failed after long runtime
Fan wire broken at the connector
Wire chewed by the cable bundle wear point
Fan disabled in firmware after a previous false trigger

How to Fix It

Identify which fan failed.

On the LCD, the error message specifies which fan: hotend (heatbreak) fan or print fan.
The hotend fan is the small one at the top of the heatsink and runs whenever the hotend is hot.
The print fan is the larger one that points at the print and only runs during certain materials.
Power off and let the hotend cool.

Wait 10 minutes for the hotend to drop below 50°C before working on the fans.
Power off completely.
The toolhead has live wires in standby on some Prusa models.
Clean the fan blade.

Use a soft brush (a paintbrush works) to clean dust off the fan blade.
Filament strings sometimes wrap around the central hub — pick those off with tweezers.
Spin the fan with your finger — it should turn freely with mild resistance.
A gritty feel means the bearing is dying.
Test by spinning manually then powering on.

Give the fan a quick flick to spin it before powering on.
Some near-end-of-life fans need a kick to start.
If powering on and flicking lets the fan run, the bearing is marginal — replace before next big print.
Replace the fan if it won't run.

Prusa sells fans matched to each model.
For MK3S+ the hotend fan is a Noctua A4x10 (10 EUR) and the print fan is a similar small fan.
Replacement is 5–10 minutes with a screwdriver.
Wiring is a small connector on the einsy board — clearly labeled.

Frequently Asked Questions

Can I disable the fan check in firmware?

Technically yes (Prusa has a setting), but never disable it.
Without the hotend fan, heat creep destroys the PTFE liner in 10 minutes.
Without the print fan, overhangs droop and prints fail.
Disabling the check buys you nothing and costs you a hotend.
Replace the fan instead.

How often do Prusa fans fail?

Prusa uses Noctua-grade fans on most models.
Expected life is 50,000+ hours, so realistically a hobbyist printer's fans last 5–10 years before failing.
If you're seeing fan failures within a year, check that the printer enclosure isn't trapping dust onto the fans, or if the print room is unusually dusty.