[aknutson]

Sorry for not knowing the correct terms. I have a vacuum diagram that I am following that I am verifying that I have all of the vacuum lines hooked up. When I first started the main vacuum junction block was popped off the heater control valve and the check valve was not hooked up. I connected both of those and chased all of the other vacuum lines and they appear to be connected. I can see the heater control valve rotate when I switch from vent/bi-level/ac/heat/defrost. I do not have any AC currently in the car except for a new evaporator and the old condenser. Where is the best place to start trouble shooting? Do the vacuum diapragms fail?

[PontGuy]

I am sure that the 72 A/C system is the same as the one on my 69. I just restored it last year so it is still fresh in my mind.

There should be a connector on top of the heater box where two vacuum hoses from the master control switch connect to the hoses that go to the two vacuum cans located behind the box. These are the cans that control the A/C and bi-level flaps. If you are lucky your connector may have just come loose. If not I would pull it loose and check that you are getting vacuum on the two hoses as you cycle the switch. In the A/C position you should have vacuum on both. If you are getting vacuum on the hoses and the connector is OK then you will need to pull the box to troubleshoot further. If you don't get vacuum there in any position then the problem is at the switch, or you are still not getting vacuum to the A/C system.

[aknutson]

The connector above the heater box was connected. I unplugged it and played with the doors and felt the air moving and plugged it my finger and the doors held open at the plastic connection that goes to the diaphragms. I did not notice any change moving from bi to a/c in the line from the vacuum source. I dont think I am getting vacuum. If I pull off the vacuum line off the carb I should feel suction?? I just pulled off a white nipple on the carb and hooked the vacuum line to it. That line goes to the check valve and then to the main vacuum to the distibution block. As I mentioned before that distribution block had been off for a while too. Also no A/C hooked up currently. Fusible link is good as well as fuse at the alternator. All fan speeds but high work currently. Good start anyways. Thanks.

[PontGuy]

Agree it sounds like your doors and vacuum cans are OK, and you are probably just not getting vacuum.

Yes you should feel suction at the vacuum source. And the fittings on the front of the carb probably won't work.

The A/C system needs to be connected to manifold vacuum. Your carb probably has a fitting on the back with a "tree" to distribute manifold vacuum to various things that need it. That is the right place to connect the A/C vacuum hose. Or you could connect it directly to one of the manifold fittings. Also make sure your check valve is installed in the right direction. If you are not sure which way it goes you can just remove it. I don't have a check valve in my car and the system works fine.

[aknutson]

I go the vacuum to work this afternoon by installing a tee at the main vacuum at the back of the carb and connected it to the check valve. All the doors open at the right setting. Pretty exciting! Now I just have the HIGH fan problem. The relay clicks, the fusable link is good and fuse is good. If the relay clicks it works...right? I will check all the contacts at the relay again. Any thoughts?

[PontGuy]

Glad to hear you have the vacuum problem solved. Assuming that your 72 is wired the same as my 69-

The relay is only used in high position. The rest of the speeds run directly off the dash fan switch through the resistor pack. If the relay clicks and the lower speeds all work fine then you know the dash switches are OK, but that doesn't mean the relay is good.

First check that you are getting power to the relay contact, it should be the black-orange wire that comes from the alternator. If the wiring from the alternator is OK and the inline fuse there is good then you should have power at the relay even with the car shut down. If you have power but the fan doesn't run when the relay clicks on, then either the relay contact is bad or you have a problem with the wire that goes from the relay to the fan. (I don't remember how the wire is routed, but it is spliced in with the output wire from the resistor pack somewhere.)

[aknutson]

I used a test light and have power at the back of the alternator but did not get any at either of the orange striped wires to the relay with the power off but I did get the light on the left orange striped wire with the ignition on accessory. There is an orange sttriped wire, white wire and then another orange striped wire looking at the relay from the front end. I see the wires come from the ambient switch, resistor and fan to the relay. The wires come out of the relay and go to the firewall where the vacuum comes out. Having trouble finding wire from alternator to relay. There is abundle from the alternator to A/C? and washer pump. I did not find the orange striped wire go directly to the relay. I'll give it a fresh look tomorrow. The wife is bugging me to watch TV now. Thanks!

[PontGuy]

The white (or gray) wire is the power to the solenoid coil from the dash switch. We know that is working because you can hear the relay click in when you set the switch to high.

One of the orange stripe wires is the power feed from the alternator and the other goes to the blower. With the ignition on you may see power on the wire that goes to the blower since it will back-feed from the resistor pack. So that is not a good check. If you don't have power on one of the orange striped wires with the ignition off then the blower is not going to run on high.

If you follow the main power from the alternator there is a wire with an in-line fuse located in the bundle that goes along the valve cover. That is the wire that goes to the relay. Have you checked that the fuse is good? Should be toward the front end of the valve cover. Seems like I remember that the wire continues on to the firewall, then through an electrical connector of some sort and then directly to the relay. Pretty sure it doesn't go back in behind the dash but I might be wrong about that.

[aknutson]

Ahhh. I chased the larger orange striped wire from the alternator to a connector like you had mentioned which looked to be attached with a bunch of A/C wires currently not attached. Put the test light on and had power with ignition off. Great sign. Struggled a bit and then found the connector unconnected coming off the relay that fit the other connector. Cleaned them up and connected and we are all good to go. My Dad had disconnected quite a few items I guess back 20 years ago when the A/C was removed. This was an excellent learning experience and appreciate all your help. I'll take a break from electrical for a while and wait til spring to get the A/C back up and running. From what I saw of the electical last night it looks like I will have my work cut out for me. Thanks again!

[PontGuy]

I just realized that you are the same guy that we were helping with the fuel/starting problem a few days ago. And then I read through your other threads.

You are doing a great job- being persistent and successfully fixing the problems one by one. Nice to have a "good student".

When are you going to post pics of the car? It always helps to see what you have when answering questions and giving advice.

Walt

[aknutson]

Yeah, I am that guy! Lots of things to get working again on those older cars. So far this year while reading and posting I took care of a shorting dash light, fuel line issue, lack of vacuum, high fan and just fixed the leak at the neck of my gas tank. I used several appication of Seal All and it worked great. Almost forgot about the fuel gauge! It's still sitting at a quarter tank and that is after a couple gallon drive and gas loss at the neck. We'll see how it reads when I fill it up. Thanks for all your help Walt.
I am waiting on a color sample to get my new package tray painted and installed in order to get the window in so I can drive it this fall. Did search on butyl tape which I bought and thought I would put the window back in but I am thinking I will have a pro do it that has experience with the older cars so the window height is set correct for the trim. So much to do and so little time!