Ok guys I bought this truck about two years ago ( 98 Ram 2500 V10 ) and ever since the day I picked up the truck I have had a issue with the Heater Blower switching from vent to Defroster at about 2000 rpm and then back to vent around 2200 rpm. the change only occurs as the rpm's are going up not down. I know that the Heater core is going out and I have had to fix a vacuum hose for the Cruse Control just after I bought the truck. My question is have any of you guys that have this model of truck or have any knowledge of said truck ever ran into this issue or know how to fix the issue? Not a big issue, more annoying then anything but would like the get it fixed if not to big of a fix. thankx

 

Check out the wild vents thread in the faq section. Basically, you just need a couple check valves in the vacuum lines, it reduces the problem, but, doesn't eliminate it completely.

 

It's not the blower motor but a vacuum leak somewhere as the vents are actuated via vacuum.