Hi, I've got a 1998 Dodge Ram 2500 4wd 360 5.9l gas. When I accelerate all the air from the blower diverts to the defrost. When I let up air diverts back to normal. I've taken ether and sprayed around everywhere I could think of looking for vacuum leak but no luck. Any ideas?
Loc: Mt. Iron/St. paul (deranged)
Probable your vacuum check valve for the HVAC. it is located on the passenger side of the plenum about in the middle. If you find the vacuum hose that goes through the firewall on the passenger side and follow that hose to the engine you should see the check valve about right where the 90 degree elbow is.
I had heard of that before but couldn't locate the check valve. I'll look again. Is that a generic vacuum check valve or a specific Dodge part, when I do a search for vacuum check valve for a '98 ram, on an auto parts store web site it returns a no parts found reply?