ddiddle Posted August 9, 2011 Share Posted August 9, 2011 In a previous thread, Rod, Jim, Mike and Mike posted a few climate control wiring and vacuum diagrams that inspired me to see if I could repair my heater/AC system, which has not worked since I've owned the car. Today, I successfully found the break in the brown power feed wire between the fuse panel and the main AC system switch, and after repairing that and then installing a new relay, everything is working correctly, power wise. However, I don't think the vacuum is working properly. Everything seems to be attached correctly behind the dash, so I found the main (solid black) vacuum line and disconnected it where it splits there by the control. Should you be able to feel or hear any sucking sound through that line, or is the vacuum produced not enough to notice with your hand or finger? As it is, I don't feel or hear anything. Also, I'm assuming this solid black vacuum line exits passes through the firewall behind the engine block, then attaches to a metal tube that runs up behind the engine and attaches to the intake manifold? Quote Link to comment Share on other sites More sharing options...
cudax Posted August 9, 2011 Share Posted August 9, 2011 Here you go. http://i304.photobucket.com/albums/nn194/mccuda/ACVACDiagram.jpg Quote Link to comment Share on other sites More sharing options...
ddiddle Posted August 9, 2011 Author Share Posted August 9, 2011 Thanks Mike - I've got this. What I'd like to know is if I should be able to hear or feel the vacuum in the black line, or is the amount that operates the mechanism not really able to be detected? I've never worked with this stuff before. Quote Link to comment Share on other sites More sharing options...
monte70car Posted August 9, 2011 Share Posted August 9, 2011 you should hear the door opening and closing when the motor is running, or at least I can on my. Quote Link to comment Share on other sites More sharing options...
wallaby Posted August 9, 2011 Share Posted August 9, 2011 I don't so much notice the doors doing anything when the engine is on... but when I turn it off, I hear the doors relaxing to their original state. Quote Link to comment Share on other sites More sharing options...
Mo's70MCs Posted August 9, 2011 Share Posted August 9, 2011 Thanks Mike - I've got this. What I'd like to know is if I should be able to hear or feel the vacuum in the black line, or is the amount that operates the mechanism not really able to be detected? I've never worked with this stuff before. Yes you should..do you have an Air Conditioning Vacuum Canister? Some of the earlier models came with a steel can (like a tin can) where others came with this style. It maintained constant vacuum to distribution vents. A booster if you will!! Possibly a leak-down test is in order, make sure you don't have a bad vacuum actuator or a split hose. A small hand vacuum pump is a great tool in this case, Good luck with it. Quote Link to comment Share on other sites More sharing options...
wallaby Posted August 9, 2011 Share Posted August 9, 2011 I think there is also a check valve in the supply line at the firewall. It can be seen in this photo right above the valve cover... right where the wires make a "V". If it's in there backwards, you get no vacuum indide the car. I don't remember there being a metal tube in this line. There IS a tube in the line that goes down to the transmission modulator, but I thought the vent supply hose was larger and rubber all the way to the engine fitting. Quote Link to comment Share on other sites More sharing options...
ddiddle Posted August 9, 2011 Author Share Posted August 9, 2011 Thanks guys. This is very helpful. Rod, yes, I've got that reservoir (the plastic one, like you have pictured), but there were no lines going in or out of it. It is just mounted there. Do you know how the routing works? Does the line go from the intake to the reservoir then from the reservoir to the check valve, then through the firewall to the control? Mark, on your intake then, do you have three vacuum lines - one going to the brake booster, a metal one to the transmission and a third feeding the AC system? Quote Link to comment Share on other sites More sharing options...
Mo's70MCs Posted August 10, 2011 Share Posted August 10, 2011 Thanks guys. Does the line go from the intake to the reservoir then from the reservoir to the check valve, then through the firewall to the control? Daryl, I believe you got it right! I'm not home to check the assy manual, although if memory serves me right. That's the way it's hooked. It only has two vacuum ports,, so I'd say it's Murphy proof! Quote Link to comment Share on other sites More sharing options...
stangeba Posted August 10, 2011 Share Posted August 10, 2011 Years ago (Mid 1970's)I was taught that a federal mandate said if the vacuum systems fail, all air will be directed to the windshield defroster for safety. Just a comment, may not help but thought it was interesting. Bruce Quote Link to comment Share on other sites More sharing options...
wallaby Posted August 10, 2011 Share Posted August 10, 2011 Mark, on your intake then, do you have three vacuum lines - one going to the brake booster, a metal one to the transmission and a third feeding the AC system? Pretty much: there is a hex fitting sticking up with 2 ports, the transmission and the vent supply. The brake booster is plumbed to the base of the carburetor. Not sure if it's weird, but mine has no reservoir. Quote Link to comment Share on other sites More sharing options...
Mo's70MCs Posted August 10, 2011 Share Posted August 10, 2011 Originally Posted By: ddiddle Mark, on your intake then, do you have three vacuum lines - one going to the brake booster, a metal one to the transmission and a third feeding the AC system? Pretty much: there is a hex fitting sticking up with 2 ports, the transmission and the vent supply. The brake booster is plumbed to the base of the carburetor. Not sure if it's weird, but mine has no reservoir. That's how the '70 assy manual shows it.... two hoses to the vacuum tee fitting. One to xmsn modulator & C60 Vacuum hose. As far as the canister I've seen some '71s with it..not seen a '72 with one ever... and most '70s, at least mine. Here is one on ebay. Quote Link to comment Share on other sites More sharing options...
ddiddle Posted August 10, 2011 Author Share Posted August 10, 2011 Thanks guys - I'm going to try to tackle this routing issue in the next day or two. Anyone know what happens if you don't have a check valve? I'd guess that all the vacuum just leaks out of the system and reservoir, so all the system doors, etc. just relax to their natural state? Quote Link to comment Share on other sites More sharing options...
wallaby Posted August 11, 2011 Share Posted August 11, 2011 I'm not sure... it might be possible that the cars had one or the other (can, check valve) but not both. I think the idea was to keep the vents from changing when you loose vacuum. It might work for a brief passing maneuver, but you'd be outta luck pulling an airstream trailer uphill at full throttle. Mine relax after about 5 seconds with a check valve. Quote Link to comment Share on other sites More sharing options...
monte70car Posted August 11, 2011 Share Posted August 11, 2011 I know when my had the a/c box I had a metal can(1970) where one hose ran to the fitting on the intake to the can and then a hose from the can to the inside of the car. Since I did away with the a/c I just tied the hose from inside of the car to the fitting every know and then you can hear the doors opening or closing Quote Link to comment Share on other sites More sharing options...
ddiddle Posted August 12, 2011 Author Share Posted August 12, 2011 Thanks for all your help guys - I got it sorted out tonight and working. Just needed the vacuum line pushed through the firewall and hooked up. In the spare parts that came with my car, I also found a water valve that I can install later. It's pretty cool to see all those little doors move with the flip of the switch...finally. Couldn't have done it without your help. Quote Link to comment Share on other sites More sharing options...
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