A fan isn't spinning: the hotend heatsink fan or the part cooling fan

Symptom

The hotend heatsink fan or the part cooling fan doesn't spin, stops now and then, or the printer shows a fan error. If the heatsink fan fails, the filament usually jams after a few layers because heat creeps up the heatsink.

Likely causes, from most to least likely

1. It isn't a fault: the part cooling fan isn't used on the first layer and, depending on the material, may spin very slowly or be almost silent.
2. Dust or plastic strands tangled in the blades.
3. A loose connector, plugged the wrong way round or into the wrong place on the board.
4. A wire broken inside the cable bundle, usually near the print head.
5. A faulty fan, or a board output or fuse that isn't powering it.

Checks to tell which one it is

• Heatsink fan: it usually starts by itself when the hotend goes above a set temperature (50 °C on Prusa i3 printers) and must spin for the whole print. Preheat and see whether it starts.
• Part cooling fan: test it from the printer menu at 50% or more, or with M106 (M107 turns it off). If it spins that way, check the cooling settings in your slicer profile.
• With the part cooling fan at full speed, move the print head from side to side several times and move the cable bundle a little: if it stops at any point, there's a broken wire.
• With the printer off, turn the blades with a finger: they should spin freely.
• Check that the heatsink fan blows air into the heatsink and not outwards.

Before you start

Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.

Step-by-step fix

1. Rule out normal behaviour

   If it's only the part cooling fan, check the filament profile in the slicer: it's usually off on the first layer and spins slowly with ABS or ASA. Test it from the menu.

   Check: From the menu it spins fine, and during the print it follows the profile.

   If that does not fix it: Clean the fan.

2. Clean the fan

   With the printer off and cold, remove plastic strands with tweezers and dust with compressed air, holding the blades so they don't spin (letting them spin in the airflow can damage the motor).

   Check: The blades turn freely and the fan starts.

   If that does not fix it: Check the connector.

3. Check the connector

   With the printer off and unplugged, check that the fan connector is in the right place on the board, the right way round and fully seated.

   Check: The fan spins when it should.

   If that does not fix it: Look for a broken wire.

4. Look for a broken wire in the bundle

   Run the fan at full speed from the menu and move the print head from one end to the other several times, also moving the cable bundle near the print head. If it stops at some point, there's a broken wire: replace the fan or the cable following your manufacturer's guide.

   Check: The fan spins without cutting out even when you move the print head.

   If that does not fix it: Replace the fan.

5. Replace the fan or check the board

   If the fan won't spin with a good connection, replace it with a compatible one. If the new one doesn't spin either, the board output or a fuse may be faulty: contact support.

   Check: The new fan spins properly.

   If that does not fix it: Contact your manufacturer's support.

Prevention

• Check and clean the fans during routine maintenance.
• Don't print if the heatsink fan isn't spinning: the filament will end up jamming.
• When fitting a replacement fan, keep the correct airflow direction and connector.

Still not fixed?

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Printers it applies to

Any FDM (filament) 3D printer, from any brand.

Official sources

This guide summarises the official documentation linked here:

• Hotend fan is not spinning · Prusa Research
• Print fan is not spinning · Prusa Research
• Err: PRINT FAN ERROR · Prusa Research
• G-Codes (M106/M107) · Klipper