Climate Control Problem
 

On my 1985 300cd turbo the climate control sytem continues to blow heat when I just have it set for fresh air. Could this be a defective monovalve or something else. The car has 82000 miles. All of the other buttons work and the air works. Just can't shut the heat off.

Heater control valve, make sure a vaccum hose did not fall off

Thanks for your reply, where is the heater valve located??