My 91 is so uncomfortable in the summer. 
Heat pours out of the dash with the heat control fully off. 
Recommendations mostly point to replacing the control valve which is a difficult process. Howes sells a deluxe unit for $90….. 
Can a shut-off valve be installed in an easier to access location. 

Many Thanks, 
Ron J 
Portland, OR 
91 Weekender, ‘Betsy’