82 - Air Conditioning...

Luster

Luster

Compulsively Anal
Joined
Mar 23, 2008
Messages
454
Location
Lee's Summit MO
This is a little complicated.

1. A/C is completely charged and full with R-12.
2. A/C blows medium-cool (about 60-64*), but not cold.
3. Fresh air vent (A/C off), blows warm all the time

I know this could be a number of things, but I'm thinking that one of the vacuum doors for heat is not closing all the way.

Any ideas on diagnosing this?
 
I'll bet the temp door is not closing- letting warm air in. Find that first. I'll bet on your car it's vacuum operated and either the hose is off, the door actuator is dead/stuck, or the vacuum switch in the control head has bit the big one.

If it's cable operated- and it may be on second thought, that it's not adjusted. YOu should be able to hear the door move and maybe see the lower hinge point. The door has been known to pop the cable off the arm on top of the heater box or get loose and just slip.

I'll bet it's something in the temp door.
 
If you look on top of your AC box on the passenger side, you will see a mechanisim like below. The vacuum connector with the white/black vac line goes to the heater core control valve underhood. If you look at wire cable, it moves an actuator bracket that has a "shoe" that pushes the plunger in to control the valve. This is the Hot/Cold lever. If anything is screwed up with this system, your heater control valve will stay open.

You should be alble to check this at the valve underhood to see if it's working (keep you from taking the dash apart).

Edit: Just saw Tims post above. This is all good information, the cable shown in my picture also operates the heater door (in addition to the plunger).

4487bd45fb7abb.jpg
 
OK, here's the gig. THe cable in Larry's picture works the heat control door. The vaccum doo-dad works the water shut-off. The cable can slip see the fat end of the cable with the end of the screw sticking out? There's a slot to adjust the cable there. AND see the slot on the bracket? another adjustment for the vacuum switch. Just enough oddball adjustment crap to make you nutz.. Easy.
 
TimAT said:
OK, here's the gig. THe cable in Larry's picture works the heat control door. The vaccum doo-dad works the water shut-off. The cable can slip see the fat end of the cable with the end of the screw sticking out? There's a slot to adjust the cable there. AND see the slot on the bracket? another adjustment for the vacuum switch. Just enough oddball adjustment crap to make you nutz.. Easy.
Click to expand...

Just go to show, if you have enough adjustments, it pretty much guarantees failure:bonkers:
 
OK guys... thanks for the responses. I'm not sure where to locate the cable and "shoe" in the picture. Is it under the console?
 
I just got threw fixing a few problems with my 82. Under the hood is the vacuum operated valve that shuts off the water to the heater core. These seem to be famous for failing. Also look under the cowl on the passenger side to see if the outside air door is closing all of the way. You might have some trash on sticks blocking the door. Next check inside on the passenger side kick panel. The recir air door is located there. If it is not opening the door on max air, the vacuum switch is probably bad. If it is not opening, just hold it open with a tie wrap to recir the air all of the time. One other item is to check the vacuum control switch that controls all of the vacuum on the AC system. This switch sometimes fails by the pin in the middle falls out seperating the to halves.

This ought to keep you busy for a while! Hope this helps!
 
Pull the pass kick panel, and check that air door. Pull out the glove box interior, and look thru there. Youll see most of that stuff.
There is also an adjustment for the heater door cable behind the console carpet kick on the pass side, right behind the heater control.
 
big2bird said:
Pull the pass kick panel, and check that air door. Pull out the glove box interior, and look thru there. Youll see most of that stuff.
There is also an adjustment for the heater door cable behind the console carpet kick on the pass side, right behind the heater control.
Click to expand...

Thanks, I suspected that's where it was. Looking forward to cool air instead of hot!! :lol:
 
If your fresh air vents are warm, check your hood seal.

Attached is a HVAC diagram for a 68, shows all of the vacuum/elec. All C3's are very similar in operation.
 

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  • 68 Corvette HVAC Wiring copy.jpg
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Hey guys... thanks for the help. Pretty sure I found the problem.

The heater control valve is not closing because the vacuum line running to it has no vacuum. I don't know if the valve is functional or not. But I do know that there is no vac in the line. I'm going to take the console sides off this weekend and see if the vac line is kinked or come off on that end.
 
Luster said:
Hey guys... thanks for the help. Pretty sure I found the problem.

The heater control valve is not closing because the vacuum line running to it has no vacuum. I don't know if the valve is functional or not. But I do know that there is no vac in the line. I'm going to take the console sides off this weekend and see if the vac line is kinked or come off on that end.
Click to expand...

If the conrol cable is not adjusted to fully engage the vacuum switch in Larrys picture when the heat is full off, it won't work. That vacuum "feed" is teed off the main line going to the a/c controls.
 
Luster said:
Hey guys... thanks for the help. Pretty sure I found the problem.

The heater control valve is not closing because the vacuum line running to it has no vacuum. I don't know if the valve is functional or not. But I do know that there is no vac in the line. I'm going to take the console sides off this weekend and see if the vac line is kinked or come off on that end.
Click to expand...

If you have a hand held vacuum pump, connect it to the valve and check it out. 10 pounds of vacuum should work. My guess is the vacuum control valve under the AC controls has come apart. While you have the side covers off, hook the vacuum pump to each line and check them out.
 
Fixed the "warm" A/C air problem. I installed a hot water shutoff valve and drained the heater core.

Oh my gosh. The A/C is now blowing out at 43*. No complaints...

I would highly recommend this for anyone who has excess heat in the cabin... :p:yahoo:
 
Luster said:
Fixed the "warm" A/C air problem. I installed a hot water shutoff valve and drained the heater core.

Oh my gosh. The A/C is now blowing out at 43*. No complaints...

I would highly recommend this for anyone who has excess heat in the cabin... :p:yahoo:
Click to expand...

That's a popular fix. I guess I have just been lucky. The vacuum operated valve has always worked for me. (Till tomarrow):huh:
 
I just logged on here to ask the same question. A/C not been an issue until day time driving at 100+ degrees here lately, jezzzzzzz.

Same dang thing on mine, going to get a manual cut off valve right now. Air blows nice and cool until engine warms and then blows maybe 75-80 degrees at best.

Plus, just cruzin around at night, always felt warm air from somewhere. never thought about the hood seal, never put back on after paint, gotta be that too.

FYI, this is an 82 also, I checked all seals and functions while dash was out, everything worked fine, (did not check vacuum on water heater control valve) but having same issues as you other guys.


You guys are great!

Thanks

tt
 
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