My 1998 SC2's heater/AC fan does not work in positions I, II or III. It only works in IV. It doesn't matter what mode it is in. This problem at first was intermittent (it would fix itself in a week or two), now it is permanent. Any ideas??Thanks.

 

Bad or dirty selector switch?

 

Might be the resistor switch on the passenger side , located on the firewall, may be dirty or bad.