Blower quits blowing AC when driving sometimes

Greg B wrote:
If the blend doors are all working, maybe the a/c evaporator is freezing up. Maybe check the freon pressures?

This happened in my brother's S10 once in a trip in high humidity. It would slowly lose flow until there was almost none. Turning the heat on full blast would bring back the flow. Each time we stopped there was a huge puddle of water from the evaporator drain.