Originally Posted by tractorerik
Truck is a 1996 Dodge Ram with the V6. The A/C blows out of the panel vents until I step on the gas, then it reverts to the defrost vents. I'm guessing that the vacuum lines coming from the manifold with the check valves are bad. It looks like there are several check valves and vacuum "t's" coming off the manifold vacuum hose. Can someone send me a picture of their vacuum check valves and routing so I can make sure I get the correct replacements. On my truck they are located on the passenger side of the firewall.
I can tell you that it is certainly a vacuum leak but to be 100% sure just do a quick vacuum test it would be wise anyways cause then you can find out if their is any engine problems not that I am saying their is but you can kill two birds with one stone. Anyway's I don't think it would be check valve I don't remember any magnum's coming with check valves the vacuum leak you might be having it probably under the dash or by the T'S that is in front of the engine hidden behind the alternator, I don't have any pictures to show but to make it cool just check every vacuum line you can find, don't confuse the EVAP with the vacuum lines.