2.5 l. 5 speed

My guess is that the 'blend door actuator' has failed and is causing your problem. My info tells me that the job on a 2000 is much more difficult than if it was a 2001. Difference is that for the 2000, you need to remove the dash assembly to get access, on the 2001 you don't. Easy on the '01. Here's a directory link for you: http://repairpal.com/mazda-repair-in-graham-texas