Eppendorf 5427R no E-FAN error
Remove fan and test with external power supply. If plastic casing is broken or cracked use epoxy and align the fan so it can freely turn.
Apply 12 Volts from the external power supply and monitor output. The O/P should resemble the signal in the image.
50% DT9.5ms, 5Vpp, 9.5 ms