Heater Problems

I own a 2000 Intrigue with a little more than 25,000 miles on it. It's starting to get cold, so I've wanted to use my heater. Unfortunately, something's not right with it: it blows hot air on the passenger side, but lukewarm/cool air on the driver's side, which is quite annoying. Any suggestions or diagnoses?

Sounds like a bad temp door. Read these Buick Regal posts for more information.

http://www.automotiveforums.com/vbulletin/showthread.php?t=228099