Replace Ender 3 Heater Block

We only need the hardware, so remove the included wiring and pneumatic coupling.

Unthread the attached coupling and pull off the heat sock to reveal the screws holding the assembly together

Loosen the two indicated screw without removing them until the electronics slide out of their holes smoothly. Do not retighten

Preheat your printer to 200-230 degrees celsius

Remove the two screws on the fan cover, and set it aside on the gantry

Consider everything under the cover to be hot until you set the printer to cool down

Unscrew the pneumatic coupling and pull off the heat sock

Repeat step 1 on the old heat block, loosening the indicated screws just enough that the electronics are loose in their slots

Set the printer to cool down to prevent a thermal runaway when you remove the electronics

Keep in mind that everything is very hot at this point

Hold the electronics by their insulation and gently wiggle them out of the heater block

The old heater block is probably still hot enough to burn you at this point, make sure to hold onto it with something that isn't your hand

Remove the two screws holding the old block to the frame, and use them to attach the new one

Holding them by the wire, slide the hopefully cool electronics into the new heater block

Using the smaller Allen key, make sure the thermistor is sitting in its slot before tightening

Tighten both screws just enough to hold the cartridge and thermistor wires in place; pull on the thermistor wire just enough to keep it under the screw head while tightening

Reattach the pneumatic coupling and heat sock, making sure that the Bowden tube is pushed all the way into the block to sit snuggly against the nozzle.

Reattach the fan cover

Make sure to relevel the print bed before resuming printing, as slight differences in the placements of the heat sinks and nozzles might change the print height