blowing fuses on 1990 Chevrolet Blazer

When going from vent to off I blow a fuse. What could be causing this problem?

Asked by for the 1990 Chevrolet Blazer
Short circuit in mode selector switch in the control panel. Part prob. discontinued. You can check. AC and other controls work ok?

Update! Try NAPA part # TEM 207465. AC mode selector switch. That lever activates this switch, will need to remove the heater control panel to replace it. Not a hard fix if a little car savvy.