1979 A/C Duct problem
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Joined: Jun 2005
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From: Independence Mo.
1979 A/C Duct problem
I finally got the a/c to work on my 1979 but know the only place I am getting air out if thru the floor vents. No air is being blown out thru the dash vents. Any help or guidance on where to start looking. Thanks Gary B.
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Joined: Apr 1999
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From: CORVETTE 77 385 C.I. TEXAS
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 theft 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. hose 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.
1) The vac. line from engine is damaged from heat - a small plastic tube that goes in below the hood theft 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. hose 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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Joined: Jun 2005
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From: Independence Mo.
I just looking under the hood of the car and found the hose you were talking about, it is running down the valley and below the screen. What I did find was a rubber plug with three hoses coming out of it. It is located behind the dist cover. One of the hoses is green and it runs under the hood switch, the black one runs behind the dist, and the white one (approx) 2ft long is blocked off. Does anyone have any idea where this hose should go. Thanks Gary B.
Le Mans Master
Joined: Aug 2003
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From: Chattanooga TN
Originally Posted by Ganey
1) The vac. line from engine is damaged from heat - a small plastic tube that goes in below the hood theft 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. hose to heater hose valve underhood probably also needs replacing. Block w/o heater.
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. hose to heater hose valve underhood probably also needs replacing. Block w/o heater.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Originally Posted by Gary B.
... the black one runs behind the dist, and the white one (approx) 2ft long is blocked off. Does anyone have any idea where this hose should go. Thanks Gary B.
The white plastic tube should be no.3.
When the vac. source is good, the car can be fired up to test. If still not good, you can press the switch under console together front to back to test switch. (2)
Pro
Joined: Dec 2002
Posts: 560
Likes: 1
From: Mooresville NC
On my 79 one of those tubes going through the firewall hooks up to the heater control valve, probably the 2ft one that's blocked off. My vote is with GANEY's #2 as it fixed my problem with the same symptoms.
Drifting
Joined: Jun 2004
Posts: 1,881
Likes: 9
From: staten island ny
Originally Posted by Ganey
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 theft 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. hose 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.
1) The vac. line from engine is damaged from heat - a small plastic tube that goes in below the hood theft 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. hose 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.
Thx ESU
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Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
ESU
The A/C VENT control is attached directly to the vacuum switch below it under console. By removing a console side it is possible to test by pressing the switch under console together front to back. (no.2)
The system is very reliable except the underhood plastic tubing (esp. for Hotrodders who increase power & heat) & the rivet holding the vacuum switch together.
Any vac. leaks can effect operation so check all vac. lines. Many times a leak will be at the attachment point, if so then cutting about 1/2" or less hose off for a fresh connection can fix. Also try bypassing the headlight vac. tank.
The vac. switch under console w/ colored hoses is easy to find.
If a pic. is needed of the vac. switch itself, I can probably come up w/ one.
The A/C VENT control is attached directly to the vacuum switch below it under console. By removing a console side it is possible to test by pressing the switch under console together front to back. (no.2)
The system is very reliable except the underhood plastic tubing (esp. for Hotrodders who increase power
& heat) & the rivet holding the vacuum switch together.Any vac. leaks can effect operation so check all vac. lines. Many times a leak will be at the attachment point, if so then cutting about 1/2" or less hose off for a fresh connection can fix. Also try bypassing the headlight vac. tank.
The vac. switch under console w/ colored hoses is easy to find.
If a pic. is needed of the vac. switch itself, I can probably come up w/ one.
Last edited by Ganey; Jul 7, 2005 at 05:53 PM.
