A/C Vacuum check valve

'96 Star, running down a vacuum issue regarding the "mix" doors and control of airflow to the floor, dash etc. I have the factory manual and the electrical/vacuum troubleshooting manual. Both have lead me to the A/C vacuum check valve, yet neither manual shows where it is located. Have you seen it? I think it might be hidden behind the intake manifold on the back side, but I have quit for the evening and thought I'd put the question out.

Thanks

Well, found it with the help of my local dealer. I called and asked about the part, and asked if their system could help me locate it. The parts guy said sure, and faxed me over a diagram. Boy was it buried: near the firewall above and behind the fresh air intake for the heat/ac system. The A/C vacuum tank is there as well. Those checked fine, but in working with them I noticed the hose that provided vacuum from the intake manifold had worn through creating the leak. I was able to affect a basic repair and all works well now.

Thanks to those who read my post.

Well, found it with the help of my local dealer. I called and asked about the part, and asked if their system could help me locate it. The parts guy said sure, and faxed me over a diagram. Boy was it buried: near the firewall above and behind the fresh air intake for the heat/ac system. The A/C vacuum tank is there as well. Those checked fine, but in working with them I noticed the hose that provided vacuum from the intake manifold had worn through creating the leak. I was able to affect a basic repair and all works well now.

Thanks to those who read my post.

Having the same problem. Can you send me a copy of that diagram??

Having the same problem. Can you send me a copy of that diagram??


Sure: [email protected] with a fax number. I don't have a scanner so that is the only way I can think of other than snail mail.

By the way, what exactly are you having a problem with?

Sorry no one was able to help before you found out but the info you passed along will sure help someone else oneday.Thanks. Gary

Sure: [email protected] with a fax number. I don't have a scanner so that is the only way I can think of other than snail mail.

By the way, what exactly are you having a problem with?


Not getting airflow through instrument panel inside van. Defrost only. Could be a vacuum problem.

Not getting airflow through instrument panel inside van. Defrost only. Could be a vacuum problem.


Ok, on the '96 my manual clearly stated that without vacuum, the default position is defrost. I don't know if you have a vacuum gauge ( I have a hand vacuum pump and it worked fine as a guage) but the vacuum accessories run at about 15"/Hg. I was getting around 4 indicated at the vacuum motors - two located on the driver's side above the accelerator, and one under the glovebox.

The vacuum source is the rear of the intake manifold (I'm tallking a 3.8L here). There is a 3/8" diameter nozzle on the back passenger side. The rubber fitting has two vacuum lines in it, one red, one yellow. The red runs from the manifold up to the vacuum check valve behind the outside air intake. From there, a short black line runs from the check valve to the tank, and an additional black line runs into the firewall near the freon line - this line carries vacuum to the a/c selector that then channels it to the vacuum motors. The two motors near the accelerator have two lines - the one with green/red is the floor/panel, the blue/yellow is the floor/defrost and the orange line runs the outside/recirc motor under the glovebox. The two line units have a 1/2 and full position depending on whether one or both of the lines have vacuum.

Since you have defrost only - no vacuum - I would start at the intake manifold and work back from there. My leak was in the red line between the manifold and the a/c vacuum check valve. I saw it rather than heard it and to fix it I cut some clear 1/4" tubing in half so I could slip it over the line and then simply taped it snug with duct tape. It holds 15"Hg just great.

Sorry for the long post - but figured you might be at it tomorrow. Let me know if I can send you that diagram - It wont tell you much more than I told you, but can give you a visual on what you are looking for. I will tell you that to get at all of that stuff I had the entire cowl off - which is really not that hard, but it takes a little while.

I'm around this weekend if I can help any more.

Good Luck

Well I just started having trouble today with the rear air. At first it w/blow at you're feet in the rear [cold]. I would mess w/the rear hot/cold knob at the far right of the knobs[98 3.8] and then it finally started blowing from overhead. When I got home I took the rear panel out and checked the actuator that moves the flap from top to bottom and it did'nt want to move very much on it's own.I then started checking the hot/cold switch for the rear in the dash. I took it apart and found out how the vacume works as it goes through it when you switch from hot to cold . Vacum going to the switch is good [checking w/out a guage] but vacume at the actuator was not.Going to replace the hot/cold switch this week.