Hi,new to the site and my problem is my heating vents wont change.They just blow defrost.It seems to be controled by air,is this true?If so were does it get its presure from?I noticed it stop working around the the time my heater core started to leak.Replaced core and still nothing.
98 ram 1500 5.9l

 

The vacuum hoses are on the passenger side of the motor. Make sure none are cracked. There are also check valves that can be bad in the same location.