Vacuum leak

[Hotroder383]

Ok so I have anothe leak, I know because when I give it more than half gas the heater control shifts to defrost. I.E. heat is on, blowing on your feet, give it gas it switches and starts blowing out the defrost on windshield.
Any common areas I should be looking into? I know GM had a bad time with the hard plastic lines under hood. I see alot of the same style lines on my Ram. Or maybe behind dash near switch?? Any hints to keep me from tearing the whole damn truck apart would help =).

 

[Hotroder383]

Ok then, whole damn truck it is then. I'll tackle it next week when I get back, and post up my findings in case someone else has same probs.

 

[rambob]

try the two check valves under the hood on the pass side. they are under $5 from the dealer.

you can pull the out and try to blow through both ends. if you can, they are bad.

it didnt fix mine, but that is what I have read is the first place to look.

 

[Hotroder383]

Thanks bob, still aint got around to lookin into this problem yet. Hopefully next week =/

 

[KdkGrizz]

Hey everyone. I would think that something like this being so common that there would be more information out there. I replaced the check valves as well on my 2000 1500, and I have the same issue. When I have vents on or A/C and the truck is under load it closes the vents and diverts the air to the defrost. I am stumped and the wife is chirping in my ear about it on long camping trips. HELP PLEASE SAVE ME!!!!!

 

[Bigtman07]

What you may not know is that there is specific order to the check valves and the vacuum lines. If they are in backwards or in the wrong order then it will still happen.