I have a 2001 ram 1500 sport. I have no heat blowing thru vents. Checked thermostat, flushed water thru heat core to check for clog, it wasn't. Took off blend door motor and checked plastic interposer ( heatertreater) it wasn't cracked. When I tried to spin the shaft to blend door it's spins back and forth freely. Shouldn't it stop when it shuts off one side?

 

Welcome to DF
Yes, the doors need to stop at some point. Did you check the recirulation mode door? I will move you post to the 2nd Gen Ram section.

 

No. How do you Check those. Thanks for moveing this. Still trying to figure out the site

 

I'd double check the vacuum lines as well.

 

Under the hood and the back of the switch in the dash looks good.

 

Took the servo motor off. Have movement in the blend door. Moved to both sides still got cold air. Guess I'm gonna be changeing heater core