Surprised there isnt a thread on this that i could find, but where do we find diagrams for vacuum lines for 1998 ram van 5.2L? My AC/heater control module is hissing, so i replaced it and its still hissing, which means either vac line is broken or something more expensive internally behind the dash (so i'll start with the vac lines first). Also, only defroster works, unless i put the **** on AC, then for some reason it blows air out the floor and face areas (until i give it a good amount of gas, then it reverts back to the defroster temporarily). Oh, and for the record..no AC, even though the clutch kicks in. I only have max heat. Its a mess and relatively annoying, so i'd like to fix it Anyway, where can i find a diagram for the vac lines that exit from the firewall into the engine bay? Thank you!

 

You have a vacuum leak somewhere. The hissing should lead you right to it, and yeah, it's likely buried back in the dash somewhere.

I think the only place you will find those diagrams, is in the factory service manual. Having one really isn't a bad idea..... and you can generally get an electronic copy for under 50 bucks.

 

My problem was the switch itself. They use a rubber diaphragm and it was bad. I still had wild vents under hard acceleration turned out to be my motor had low compression

 

Yes this sounds like a good idea. I will try to find one. As for the hissing, its right behind the actual ****. Even the new replacement did it, which is why im looking into the vacuum lines next

 

Yeah if its not the vac lines, then its something behind the dash that is a pain to get to. Something to do with a motor that controls the flow/direction of the air (hopefully it isnt that)