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Old 07-11-2008, 11:51 PM   #1
MosportGreen66
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Default 1979 Corvette A/C Question

Now that we have the Air Conditioning working in the 79; is the A/C supposed to blow out of the top vents? Or blow out of the bottom of the dash?

Thanks,

-Dave
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Old 07-12-2008, 08:38 AM   #2
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It's suppose to blow out of both as per the HVAC control panal. There are marking showing up down and both. at least mine did.
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Old 07-12-2008, 09:44 AM   #3
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I Dont Know My A/c Dont Work
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Old 07-12-2008, 05:11 PM   #4
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It was a long time ago ....hmmmm.... BOTH
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Old 07-12-2008, 07:27 PM   #5
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Default 79 Ac

mine blows out above the gauge bezel and the side vents. It does not blow out where the heated air would blow below or out the defroster vent.
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Old 07-12-2008, 10:38 PM   #6
blk79nj
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My '79 blows out the vents that on top of the gauges, and the one that is by your left leg when you are driving.
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Old 07-12-2008, 11:56 PM   #7
MosportGreen66
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Ok it seems I have a problem. No Cold Air blows out of the vents above the gauges. It only blows down by the driver's and passenger's feet. Any idea's what this could be?
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Old 07-13-2008, 07:23 AM   #8
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I'd say the ducts that feed the air up are either disconnected or blocked. I opened up a Toyota dash one time and the vent was totally blocked by a rat's nest. It was full of insulation from the car, drinking straws, paper, lots of junk. Most likely, someone has removed part of the ducting, maybe for stereo clearance. Or maybe they just didn't notice it was loose.
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Old 07-13-2008, 08:20 AM   #9
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I wrote this up awhile back for this problem.

On at least later C3 the problem is that heater is the default position (no vac. or vac. leak) due to being designed in the north. Vent should be default. Very safe bet the problem is 1 OR 2:
1) The vac. line from engine is damaged from heat - a small plastic tube that goes in below the hood alarm switch into wiper valley. Replacing most of engine side w/ hose will fix. OR
2) The vac. switch itself is not switching due to vac. leak as the usually plastic rivet is not holding the 2 main switch parts together well. Besides replacing, it is also possible to tighten this &/or lube w/ a thin layer of white lithium grease or vasoline to fix.
3) If you have a heater, the small vac. tube to heater hose valve underhood probably also needs replacing. Block w/o heater.

PS The design problem comment is not intended to be offensive to any of our northern friends.
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Old 07-13-2008, 12:09 PM   #10
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Quote:
Originally Posted by MosportGreen66 View Post
Ok it seems I have a problem. No Cold Air blows out of the vents above the gauges. It only blows down by the driver's and passenger's feet. Any idea's what this could be?
Sorry, I mixed up your question with the post by cruise83 about lower vents. If it's coming out by your feet, then it probably is in either the vacuum or actuator that moves the air flow as Ganey says. I thought your cold air was coming out the lower vents (not the heater vents) when I answered.
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Old 07-13-2008, 11:21 PM   #11
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Thanks for the replies guys. I appreciate it. I'll keep you up to date on what I find.

Thanks,

-Dave
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Old 07-14-2008, 05:23 PM   #12
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Default I would like to know as well

Is there a specific spot to view a diagram of the internal vacuum hoses? My '78 has similar issues. I have no vacuum at the heater hose valve under the hood. So I am working backwards.
Please post info as you get this figured out. Thanks
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Old 07-14-2008, 06:08 PM   #13
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Quote:
Originally Posted by bn2wild View Post
Is there a specific spot to view a diagram of the internal vacuum hoses? My '78 has similar issues. I have no vacuum at the heater hose valve under the hood. So I am working backwards.
Please post info as you get this figured out. Thanks
One used from Dr. Rebuilds web site I dolled up with correct hose color codes.
Click the image to open in full size.
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Old 07-14-2008, 10:42 PM   #14
bn2wild
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Default Finally info for that pesky air vent not working!

Bmotojoe you are my hero!!
I really appreciate this! Between your diagram and the following one I will share here, I actually found my leak. It was the tiny 1/8" air supply through the firewall, somehow had burned and sealed it's ends near the tee.

I feel that including this diagram for others, that they may find this post in the future...

Click the image to open in full size.
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Old 07-15-2008, 10:04 AM   #15
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i just had to fix mine yesterday, the AC air was blowing out the vents on the floor, the three small plastic hoses that exit out the grommet on the fire wall were broken, brittle from engine heat. i was able to remove the glove box and push the hoses through so i could reattach them with some small vacuum tubing. (temporary fix), order new vacuum tubing kit from zip. i believe with no vacuum it defaults to the floor. it could also be the vacuum rotary switch underneath the console ac control panel. i had to replace that also last year. thats a good pic there bmotojo
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Old 07-24-2011, 03:38 PM   #16
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I didn't want to start a new thread as the OP's problem is the same as mine. I know it is a vacuum problem. It is too hot out in the garage to work on anything and I wondered if there is anyway to force the air to come out of the dash vents as a temporary fix until it the weather cools off a little.
The vacuum control switch/valve seems to move freely but, rotating it does nothing.

Thanks Rick

Last edited by Rick_V; 07-24-2011 at 03:42 PM. Reason: More info.
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Old 07-25-2011, 09:52 AM   #17
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Looking at the schematic from my AIM it looks like only ONE (black hard plastic) of the three lines coming through the firewall goes to manifold vacuum, one goes to the heater water control valve (clear) and the other (green) goes to the passengers side to I believe the bi-level control (not sure don't have the AIM in front of me). Well on mine the small black hard plastic one goes to vacuum but so does the clear one into a "Y" and the green one goes to where it should. Could the fact that the PO hooked this up wrong be the root of my problem?
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Old 10-26-2011, 10:58 PM   #18
travelerbob
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My 79 has the same problem I think. Have vacuum to heater control valve in heater hose. Fan works but vent, heater, def. does not change pos. You should be able to hear the sound of the air when it changes positions. It seems that the air is comming from the floor outlets but not 100% some from def. Any ideas to look for??

Last edited by travelerbob; 10-26-2011 at 11:00 PM. Reason: additions
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Old 10-26-2011, 10:58 PM
 
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