Heater fan again

[AJPL]

Heater control unit fried the wiring loom a few months back but cutting the loom back and replacing the connector sorted that out. The fan has just stopped working again but the wiring and connector are pristine this time.

if i bypass the switch and control unit the fan functions fine so i know that works. Firstly how can i test the switch to see if that is faulty. Secondly, if it is the control unit again, is there anyone out there who can repair it or can it be bypassed to give a permanent low speed fan.