Heater fan control...

[Hedgehopper]

When I went to start the engine yesterday there was a loud groaning/buzzing noise as soon as I turned on the ignition. After a worrying five minutes I traced the noise to the passenger footwell adjacent to where the heater fan motor is hidden behind the vertical carpeted area. When I pulled the rotary fan control switch out (I believe this activates the heated mirror function) the noise stopped but with it pushed in the noise restarted and so did the fan itself.
In a nutshell, with the rotary switch pushed in, fully anti clockwise and ignition on the noise starts. as I turn the switch clockwise the fan runs normally.
Anyone any ideas as to what is going on? Help appreciated.

[Belle427]

Sounds odd but I’d concentrate on testing the switch first, maybe the contacts have failed internally.

[pits]

Mine does similar, sounds like a dying giraffe, comes and goes as it pleases haven't traced why it does it.

[Loubaruch]

Could it just be a worn fan bearing that is only noisy with the fan rotating slowly, when speeded up the fan spindle may ride up onto a quiet part of the bearing.

[Hedgehopper]

Thanks guys for the suggestions, I will look into this further but not until the end of the week. Just hoping I don’t need to take the motor out!