#21  
Old 05-14-2014, 07:48 AM
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Quote:
Originally Posted by gburbage4 View Post
From the "Ä Problem Well Stated Is Half-solved" file: I drove my car today and noticed that warm air only comes into the car while it's moving. If I'm stopped, nothing flows. It may be the door cable after all.

As for the flow-through ventilation, it must be a really low speed.


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Sounds like the blower motor is not working. The gravity is allowing the air flow while driving.

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  #22  
Old 05-14-2014, 08:18 PM
gburbage4 gburbage4 is offline
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Originally Posted by indymanjoe View Post
The fan shouldnt be running in off.That has nothing to do with the actuators.Do all the fan speeds work correctly?
Yes, they do.

  #23  
Old 05-14-2014, 08:19 PM
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Originally Posted by 2002Z4CSS View Post
Sounds like the blower motor is not working. The gravity is allowing the air flow while driving.
I should've added this happened yesterday with no climate control operating, except for open windows.

  #24  
Old 05-19-2014, 12:15 AM
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I completely re-worked the system in my 69 during restoration a few years ago and learned a bunch about it. Before the repairs I always got a bunch of heat coming into the car- not good when you live in Georgia.

The way that the 68-72 "flow through" A/C system is designed there is always an open path between the heater core and the car interior. The dampers control where the air goes and how much fresh/cooled air is blended in, but they do not isolate the heater core. Instead the system uses a vacuum-operated water cutoff valve to keep hot water from flowing through the heater core when the lower slider is in the far left (cool) position. A vacuum switch located behind the controller closes the valve. If the water cutoff valve is missing or not working then you will get heat in the car no matter what. You should see the valve mounted on the top front of the suitcase under the hood.

The fan speed position switch does not shut the fan off. But the main selector slider has a switch that cuts power to the system when in the "off" position (far left).

If everything is intact and working right, with both upper and lower sliders in the far left position the fan should not run and there should be no heat. So first thing to do is to try driving the car with the sliders set that way. If you get heat then the water cutoff valve is not closing.

In my case the water cutoff valve was bad, and water/antifreeze must have got sucked into the vacuum line because the vacuum switch behind the controller assembly was ruined. Sourcing up a new valve and a new vacuum switch was quite a challenge, but getting it working properly eliminated the heat in the car- except when I want it.

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Last edited by PontGuy; 05-19-2014 at 12:37 AM.
  #25  
Old 05-19-2014, 12:24 AM
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Also worth a mention- the norm/vent switch just turns the A/C compressor on and off.

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  #26  
Old 05-19-2014, 05:41 AM
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Thanks PontGuy. That is great information.

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Old 05-19-2014, 08:07 PM
gburbage4 gburbage4 is offline
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Quote:
Originally Posted by PontGuy View Post
I completely re-worked the system in my 69 during restoration a few years ago and learned a bunch about it. Before the repairs I always got a bunch of heat coming into the car- not good when you live in Georgia.

The way that the 68-72 "flow through" A/C system is designed there is always an open path between the heater core and the car interior. The dampers control where the air goes and how much fresh/cooled air is blended in, but they do not isolate the heater core. Instead the system uses a vacuum-operated water cutoff valve to keep hot water from flowing through the heater core when the lower slider is in the far left (cool) position. A vacuum switch located behind the controller closes the valve. If the water cutoff valve is missing or not working then you will get heat in the car no matter what. You should see the valve mounted on the top front of the suitcase under the hood.

The fan speed position switch does not shut the fan off. But the main selector slider has a switch that cuts power to the system when in the "off" position (far left).

If everything is intact and working right, with both upper and lower sliders in the far left position the fan should not run and there should be no heat. So first thing to do is to try driving the car with the sliders set that way. If you get heat then the water cutoff valve is not closing.

In my case the water cutoff valve was bad, and water/antifreeze must have got sucked into the vacuum line because the vacuum switch behind the controller assembly was ruined. Sourcing up a new valve and a new vacuum switch was quite a challenge, but getting it working properly eliminated the heat in the car- except when I want it.
PontGuy, the hot air comes in with the controls set the way you described. Funny in the winter, with the heater running and the car not moving, cool air comes in. Is that also a symptom of the same problem?

Thank you very much for the thorough explanation; even my non-automotive-oriented wife understood it.

  #28  
Old 05-19-2014, 10:16 PM
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Yeah that was the simple "wife-friendly" version. Getting into the details things are a bit more complicated

Quote:
AC/Heater system-

I haven't gotten to prying the knobs off the control yet but did take some time tonight to figure out how it all works. Good thing I did because at least a pair of the vacuum hoses were hooked up backward, which explains why my bi-level never worked right. For those that are interested here is what I learned:

There are four vacuum cans that operate dampers in the vent system. All of these are controlled by the upper slider through a multi-position vacuum switch. The vacuum can in the passenger's side kick panel controls whether air is recirculated or whether fresh air is drawn in from the cowl. It has two vacuum hoses connected to it (more about this in a bit). The vacuum can at the left end of the heater box controls whether air is directed to the lower heat vent or the defrost duct. There are also two vacuum cans behind the heater box. When the lower one opens its damper it directs air to the dash (A/C) ducts. When the upper one opens its damper, it too directs air to the dash ducts, but the upper damper also blocks air from going to the heater/defrost when in the open position. In the closed position air is free to travel through the system to the heater/defrost damper.

The bottom slider actuates the main damper and the vacuum switch for the water cutoff. In the hot position all of the air is directed through the heater core. In the cold position all of the forced air is directed around the heater core. But even in the cold position the heater core is not isolated- there is still an open path from the core to the heater outlet. So the system relies on the water cutoff to completely shut off the heat.

Back to the top slider.

In off position vacuum is cut off from all of the vacuum cans. This leaves the fresh air damper in the recirculate position (no fresh air). The heat/defrost damper is in the heat position and both of the dampers behind the box are closed, sealing off the A/C ducts but keeping the path to the heat/defrost damper open.

In the A/C position vacuum is directed to all the cans. That means 100% fresh air is drawn in, and both the upper and lower dampers direct air into the A/C ducts.

In heat position vacuum is directed just to the two hose connections on the fresh air can in the kick panel so that 100% fresh air enters the system. Remember the path to the floor heat vent is wide open as the default, even with the system off.

defrost position is the same as heat except vacuum is also applied to the heater/defrost damper which directs the air into the defroster vent.

In bi-level position vacuum is directed to the lower damper which allows air into the A/C vent system. The upper damper stays closed so air can also pass through to the floor vent. (I found my hoses for the upper/lower cans were reversed, so that bi-level only allowed air to the A/C vents through the upper damper.)

The kick panel vent is fully open so that 100% fresh air enters in all of the above operating positions. In inside position however vacuum is only directed to one of the connections on the can (remember there are two hose connections) which partially opens the damper. So there is actually a blend of inside and outside air, and otherwise everything is the same as AC mode. I was surprised to discover this- and it leads to a question. As my system was hooked up vacuum was applied to the middle hose connection on the can, which opens the damper about 80% (meaning 80% of the air would still be fresh.) By swapping the hoses so that the vacuum is applied only to the secondary connection on the can the damper will only open about 20%, which means 80% of the air would come from inside the car. To me this makes more sense for inside position on the control.

I haven't traced out all the electricals but that looks pretty straightforward. There is a master switch that engages power to the system in all positions but off. The fan switch directs power to the master relay and selects the appropriate resistors in the engine bay. And it looks like the norm/vent switch is just a cutoff for the compressor- there are no electrical connections to any of the dampers so it can't affect airflow.
And a link to the thread that I ran when I was going through all this: http://forums.maxperformanceinc.com/...=638353&page=2

From what you describe your cutoff valve may be frozen. Easy to check if it's working- with the system in cool position the heater hoses at the valve should not be hot since the valve should prevent water from flowing through them. Then if you push the lower slider to the right the valve should open and the hoses should quickly get very hot.

Also if you are getting a lot of air with the fan off, then maybe the fresh air damper in the kick panel is not closing. Easy to check that too. Just pull the passenger kick panel and watch what it does in the various selector positions. It should be fully closed with the system off.

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  #29  
Old 05-19-2014, 10:31 PM
gburbage4 gburbage4 is offline
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PontGuy, thank you for the suggestions. Worth doing of the Memorial Day weekend!

  #30  
Old 05-19-2014, 10:39 PM
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My 72 Luxury Lemans does not have that cutoff valve.I have not seen one on an A-body 72 era,some F-bodys i have noticed it on.Tempts me to install a manual valve on the supply side to the heater core though.

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  #31  
Old 05-19-2014, 11:15 PM
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Hmmm, I know that the heater box is the same and the control system is the same. And I owned a 71 and a 72 that both had the valve. So did a bit of searching and found this:

http://thepartguy.com/ac-controls-gtolemans.htm

Looks like they eliminated the valve mid-72. Not sure how they kept the heat out- probably didn't.

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  #32  
Old 05-20-2014, 01:12 AM
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I had a 72 GTO back in the early 80's - so this is from old memory - but I remember it working as someone previously described - the fan always runs... and so the cool-warm selector is always active in terms of determining what type of air enters the car - even with the top lever all the way left.

The '69 description is a good one - but I think the system design was changed between '69 and '72 so those details may not hold for '72.

If you are still getting hot air in at your feet when the bottom lever is full left, its likely just a stretched cable and/or bad flapper door and/or misadjusted cable... the door may not be snapping all the way closed when the lever is full left. There is a detent in the heater box that functions to snap it closed and seal it - good chance that detent isn't being activated.

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  #33  
Old 05-20-2014, 08:33 AM
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Nope, the systems are identical through 72 (except for late 72's not having the water valve which I just learned about myself.) The 69 I have now was just the first time that I went all the way through one of these systems and figured it all out. If you open the link everything being sold there matches with my experience over the years. And they have some great pictures. I wish I had found that site when I was rebuilding mine because they look like an outstanding source for hard-to-find parts.

In fact I have a pristine (rebuilt) 70-72 controller assembly that anyone here is welcome to for free if they need one. Laid side-by-side I found it to be exactly the same as the one in my 69 except for the angle of the face plate. I stole the water valve vacuum switch from it but otherwise it is complete, including the switch that shuts power to the fan in off position.

There is a lot of confusion out there about how the A/C system works. It is not at all obvious and I guess not many have done a complete tear-down like I did. Also the non-A/C box is altogether different which adds to confusion. Bottom line is that the cable-driven flapper door diverts air coming into the box from the suitcase, one way through the heater core and the other way bypasses it, but does not isolate it. In either position the heater core is open to the heater vent even with the system full off. Crazy design if you ask me.

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  #34  
Old 06-07-2014, 11:23 PM
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Quote:
Originally Posted by PontGuy View Post
Hmmm, I know that the heater box is the same and the control system is the same. And I owned a 71 and a 72 that both had the valve. So did a bit of searching and found this:

http://thepartguy.com/ac-controls-gtolemans.htm

Looks like they eliminated the valve mid-72. Not sure how they kept the heat out- probably didn't.
Well, I finally removed the glove box and kick panel (which was a pain), but didn't see anything obvious. I did notice that if I turn on something and the small slider underneath moves, the hot air stops flowing in.

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