I had a similar problem. Hot air coming out of window vents and hot air coming out of defroster vents all the time. Fuse looked fine, I just suffered like that for a while.
Last week I decided to tackle the issue. Read about testing the monovalve.
I was advised to turn the key to the on position car running or not and unplug the monovalve to see if i could feel a click, i didnt feel a click, but it was pretty hot. Tried to measure resistance for the monovalve, but I may have done it wrong.
I have a small multimeter from Sears. Set to Ohm 20k (changed from 20M to 200 - trying to get a reading), cross neg/pos get zero, place the neg/pos terminals on the monovalve two connection terminals and get zero (so I guess I am doing it wrong - cannot tell what the resistance is) however then used it to test the voltage of the connector that plugs into the monovalve and it was zero too. (i guess i was able to use it fine for that).
Turns out fuse #7 had a tiny crack which i guess i missed - replaced it and no more hot air (ac doesnt work - different issue). Tried to test the monovalve again, still couldnt hear it click and was not able to get any different results with the multimeter, but no more hot air.
What does open mean? does open mean zero?
Any pointers on how to utilize the multimeter? Maybe i was doing it correctly?
http://froogle.google.com/froogle?q=sears+multimeter+82082&hl=en&lr=&sa=X&oi=froogle&ct=title
Thanks