A have that strange ticking noise coming from behind the air temperatuire control switch on my dashboard.

The ticking stops depending on where the air temperature control is set. At full cool the ticking is present, at the 12 o'clock position the clicking stops.

The temperature of the air coming out of the vents does change with the position of the control.

Where might the ticking be coming from and how would I go about fixing it.

Thanks.