My heater on my 97 3.8 coupe is stuck on defrost. Since it is pumping out warm air is it safe to assume the control switch assembly in the dash board needs to be replaced?

 

That is a vacuum problem. It defaults to dash defrost. I'd check around the vacuum lines under the hood around the driver's side.

EDIT: I meant to say look for a leak in them.

 

Thanks for your input. It saved by a bunch of money and was an easy fix. Cost me 65 cents for a rubber tube splice that fit over the line that had broken in two. For anyone with this problem is a line about the size of a pen refill that runs from a plastic vacumn manifold that is near the master brake cylinder.

 

Awesome! You're very welcome. Glad it was so cheap and you found it quickly. My heat was stuck like that all winter once. I could see where I was going but my feet and legs were froze when I got there