I have a1997dodge ram van 2500 3.9 v-6 im working on it by myself and my vacuum lines all dry rotted or mouse eaten .the van sat abouy 5 yrs i cannot figure out where the lines go theres 4 lines coming through the firewalltwo go up along the firewalland around and behind the passenger headlight i have them hooked up properly i dont know where the other two go or what and where they hook up to. If anyone can help me out with a detailed pictureor diagram id greatly appreciate it. Its awful hot driving without my a/c working

 

The vacuum reservoir is behind the passenger headlight. Are there two vacuum lines going to it? If not those might be your missing two.

 

ihave those two hooked up iys the oyher two i cant figure out

 

Looking at a '96, there are four vacuum lines that come through the firewall. All snake above the PCM. The colors are faded and dirty. The two longest lines go to the fresh/recirc air door actuator behind the passenger headlamp, in front of the heater/AC core housing, next to the receiver-dryer. The colors look like black/light grey. The light line goes to the back, the dark line to the front.

The two other shorter lines look like a light and dark olive. The lighter goes to a vacuum valve on the heater hose. This line has a female-female adapter - a short length of rubber hose. The darker line goes behind the heater hoses, above the air intake duct, and connects to the vacuum supply line running back to the manifold. This line has a small plastic female-male adapter. The vacuum reservoir line connects to a 45 tee back near the manifold. NONE of the four lines coming through the firewall connect directly to the vacuum reservoir.

The manual does not have a good diagram.