New to the board, just traded a zr2 blazer for a 97 dodge ram 2500. I love the truck, but a few issues i need to work out with it. I don't have HVAC controls due to a leak in the vacuum system somewhere. I located a hard line that was broken and did some research and found out the other end was next to the AC lines. I verified the broken line on the vacuum side does pull vacuum. I dug it out, and put a coupling on it. That didn't seem to fix my HVAC issue. I'm wondering what that line goes to. If it IS for the Hvac system There may be some debris in it that needs cleaned out. Any ideas on how to go about doing that?

 

There are two that sorta disappear into the dash, one is for the vacuum reservoir, the other goes to the control head. They are both pretty much in the same area.

Line may be broken inside somewhere as well. You can pull the bezel, and heater controls, check and see if you are getting vacuum there.

 

good idea. i'm also reading the wild vents thread as i type this. that may help. I don't think I have cruise control either. light comes on but no cruise control. also the wiring is a nightmare on this truck but thats a whole other thread.

 

Several other threads.... I swear the engineers were on crack when they designed these trucks. Some of the stuff they did just makes me shake my head.....

Cruise servo is under the battery. Batteries seem to like to drip crap on them, which eats them up, and they stop working. A significant vacuum leak for the source vacuum for the cruise would give you some strange behavior.... Should be a diagram under the hood for vacuum line routing. It's a place to start at least.

 

thanks for your replies. I was an avid reader of the zr2 forums as well due to several notorious issues. Had hvac vacuum issues in that vehicle too.

 

But we have something better than any zr2 forum! If you go to the FAQW/DIY section, you can download the factory service and parts manuals for your Ram!

Welcome to DF!

 

thanks guys, put a smaller diameter coupling hose on and HVAC came back to life. still shifts to defrost at high RPM probably due to the coupler still being a smidge too big. thanks again!

 

there are two check valves in vacuum lines before they disappear into firewall. About 10.00 at dealer. Will cure the vents switching when you get on it.

 

Don't forget to also check the line that goes to the cruise control servo motor, under the battery tray.