Haunted blower fan switch

[buzzsaw]

The blower fan switch on my '97 Chimaera seems to have a life of its own. When switched off, the fan still runs at a constant low speed, not effected by rotating the knob. It still seems to work OK when switched to the on position. Basically, I can't switch the damn thing off! Any body else had this problem? How do I fix this? Thanks in advance.

[rct]

Exactly the same problem on my '98 Chim!