Blower motor

you most likely have a vacuum leak. The hard plastic lines used by manufacturer become very brittle and crack, i found that splicing them in with rubber hose pieces is better. I had the same issue on my 97 ram, and my cruise wasn't working properly either, found a badly cracked vacuum line on drivers side front of the truck under headlight assymbly area (under hood of course lol) just my two cents hope it helps

I also have the same problem with my ram 3500, and would like to know the answer. drifter354@yahoo.com Thanks Gary