I took the day off and thought I would tackle the job of finding out why my AC comes out though all vents. I read all of the old posts refering to AC. Most of them say it will be a problem with the cone shaped check valve. Most of the posts say that there are 3 lines running of this valve one to the vacuum canister, one from the the source on the manifold and the other to the passenger side of the firewall to feed the climate controls. My check value has a stopper on the side which I assume everyone says runs to the inside of the cabin. It looks like it has been ther since day one (I have an 88 by the way). I took out my trusty shop manuel and it has a wonderful diagram of the Vacuum system explaining all the color codes for the individual ac doors. However, as far as the source goes it just says vacuum source and does not say where that source comes from. Now I assume it must come in on the drives side near the resister board as all the vacuum lines run to it. ( I have one open vacuum port on this couper/switch by the way don't know if it should be open or not). So I tried to trace a vacuum line which would run to that area, the only one I see goes to my cruise control, then a larger vacuum line runs out of the cruise and down under the power brake booster. Could this be the source? If it is I disconnected the line and I am not getting a vacuum out of it from the cruise control side ( of couse this may have nothing to do with the AC and vacuum only flows if the cruise is on) by the way my cruise was working great before this hope it still works after this. Any help would be very much appreciated. To sum up my Rant where does the vacuum source for the AC doors come from on a 88 with the electronic climate controls????
Thanks in advance
Gary :confused:

 

There should be a decal on the radiator showing vacuum routing. A/C is from the right side of the plenum (near the FP regulator) to the check valve where is splits to the A/C (through the firewall behind the left head), and to another tee where it splits to cruise and the vacuum tank in the left headlight well. If the vacuum tank is leaking or defective, cruise will be intermittent or inoperative, but it can effect A/C too. Vent only is usually a bad programmer or solenoid. No vacuum generally gives defrost only. Good idea to check source to the progammer though.

 

Looking at the vacuum schematic in my '88 GM Shop Manual I see that the "vacuum source" says to "see Detail A"...which is absent!

However in the Exterior Vacuum Line Routing illustration it shows a "T" below the brake booster in connecting the line from the vacuum canister to the line from the cone shaped fitting. This "T" is labeled Vacuum Source and may be the place where vacuum is routed through the firewall to the HVAC controls.

 

Actually the vacuum line runs from the back of the motor, through the passenger side pass through in the firewall just behind the Passenger side head. It then travels across to the Programmer. If you look along the firewall you may be able to see the Vacuum line. the Vacuum source for the Ac is wrapped in with the wiring so it may be a bit harder to find.

 

Guess my Vette's an anomaly - the only thing through the firewall on the passenger side is the ECM harness. There is an orange vacuum hose in the compartment to the passenge side with a vent spliced to it - it's to the fresh air door.


[Modified by SunCr, 10:47 AM 10/21/2003]

 

LOL, Well I just told my findings when I yanked the 89 Dash and Engine harness for that from a 91. The Vacuum hard line from the Engine to the dash was also Black

 

Well, thanks to the forum Everything is working great!!! I no longer have ac coming out of all the vents. It now works perfectly. I was still not able to find where the vacuum line came through the firewall but after digging around under the passenger side of the dash, I found the black vacuum line which was bundled with some wires. I rand a temp vacuum line and spliced into the black line and bingo! it worked. So I ran my own vacuum line through the firewall and connected it the existing black line and everything is right with the wolrd :yesnod: for now. While I was under the hood I noticed that a bolt that hold the air pump on appears to be missing. I will take some pictures later and ask for more help but here is a great big Thanks! :party:

 

LOL, Well I just told my findings when I yanked the 89 Dash and Engine harness for that from a 91. The Vacuum hard line from the Engine to the dash was also Black


An '89 harness from a '91????