1977 A/C Vacuum Question
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
1977 A/C Vacuum Question
Hi All,
I was able to get my heat & A/C working today!!!!!!!
But, the blower is only coming out from the lower ducts by the center console sides. I hear a hissing from behind the dash. Are the upper to lower A/C & heater ducts controlled by vacuum lines?
If so any advice on a path to correct this?
Thanks
Jack
I was able to get my heat & A/C working today!!!!!!!
But, the blower is only coming out from the lower ducts by the center console sides. I hear a hissing from behind the dash. Are the upper to lower A/C & heater ducts controlled by vacuum lines?
If so any advice on a path to correct this?
Thanks
Jack
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
I wrote this up awhile back for this problem. No.2.
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 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.
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 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.
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
I wrote this up awhile back for this problem. No.2.
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 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.
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 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.
Thanks G,
Us Blue coats need A/C too.
Q: What about the air leak that I hear from behind the dash? Could that be the culprit?
Thanks
Jack
Last edited by xkeots; Jun 14, 2009 at 11:12 AM.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
The "air leak" if under console is probably the switch leaking- No.2 above.
If the "air leak" is behind speedo/tach panel check hoses for the manual over ride switch for the headlights at bottom of speedo/tach panel & headlight switch.
Then start w/ No.1 above for A/C Vents.
If the "air leak" is behind speedo/tach panel check hoses for the manual over ride switch for the headlights at bottom of speedo/tach panel & headlight switch.
Then start w/ No.1 above for A/C Vents.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
This vacuum chart says for 1980 but it is the same on the 1977 with AC cars. We need to update the year on this. The hose colors are the same, the function chart is the same.
http://willcoxcorvette.com/repairand...lp.php?hID=273
Here is the switch that may be leaking. It is held together with a plastic rivet. All that keeps this sealed up is the pressure of this rivet and it can break real easy. If your switch is not damaged, an old trick was to blow a little bit of oil in the switch to help it seal. May/may not work but it might be worth a try.
http://willcoxcorvette.com/repairand...lp.php?hID=273
Here is the switch that may be leaking. It is held together with a plastic rivet. All that keeps this sealed up is the pressure of this rivet and it can break real easy. If your switch is not damaged, an old trick was to blow a little bit of oil in the switch to help it seal. May/may not work but it might be worth a try.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
I just posted a new chart that is good for all 1977-1982 cars with air conditioning. It also includes the testing chart for the heater control.
http://willcoxcorvette.com/repairand...lp.php?hID=273
Willcox Inc.
http://willcoxcorvette.com/repairand...lp.php?hID=273
Willcox Inc.
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
I just posted a new chart that is good for all 1977-1982 cars with air conditioning. It also includes the testing chart for the heater control.
http://willcoxcorvette.com/repairand...lp.php?hID=273
Willcox Inc.
http://willcoxcorvette.com/repairand...lp.php?hID=273
Willcox Inc.
Jack
PS Is there a schematic for the A/C route?
Last edited by xkeots; May 30, 2009 at 08:16 PM.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Yes, but I'm out of town and don't have it here. Maybe someone has a copy of hte schematic and can post it for you.
Willcox
Willcox
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Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
The "air leak" if under console is probably the switch leaking- No.2 above.
If the "air leak" is behind speedo/tach panel check hoses for the manual over ride switch for the headlights at bottom of speedo/tach panel & headlight switch.
Then start w/ No.1 above for A/C Vents.
If the "air leak" is behind speedo/tach panel check hoses for the manual over ride switch for the headlights at bottom of speedo/tach panel & headlight switch.
Then start w/ No.1 above for A/C Vents.
How many different girth vacuum lines are there and do you know how many feet of each size will I need to replace them and re run them all?
I have the AIM and the Factory service manual. Does either have diagrams of the routing of the vacuum system lines?
Thanks
Jack
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
do you have the cd aim? Here are the page numbers on the printed book, if you have the CD do a quick entry with two pages lower (in other words page 121 printed is 119 in the Cd).
Page 121 in the book will show you the rh vacuum can, this is where the orange hose goes. Page 122 in the book, this is where the green goes, Page 129 item number 3 is where the blue hose goes, Page 130 is whee the black and white hoses go (also pictured in 129). The ac air valve the tan hose goes to is located behind the air box on the driver side. (good luck reaching this one).
Yes you can use generic hose, and I always used a 1" section of tiny copper tubing (same size as the oil pressure tube on the older cars) between the old hose and the new one when making a connection. I would glue them together on top fo the tube so I knew they would not come off.
Willcox
Page 121 in the book will show you the rh vacuum can, this is where the orange hose goes. Page 122 in the book, this is where the green goes, Page 129 item number 3 is where the blue hose goes, Page 130 is whee the black and white hoses go (also pictured in 129). The ac air valve the tan hose goes to is located behind the air box on the driver side. (good luck reaching this one).
Yes you can use generic hose, and I always used a 1" section of tiny copper tubing (same size as the oil pressure tube on the older cars) between the old hose and the new one when making a connection. I would glue them together on top fo the tube so I knew they would not come off.
Willcox
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
do you have the cd aim? Here are the page numbers on the printed book, if you have the CD do a quick entry with two pages lower (in other words page 121 printed is 119 in the Cd).
Page 121 in the book will show you the rh vacuum can, this is where the orange hose goes. Page 122 in the book, this is where the green goes, Page 129 item number 3 is where the blue hose goes, Page 130 is whee the black and white hoses go (also pictured in 129). The ac air valve the tan hose goes to is located behind the air box on the driver side. (good luck reaching this one).
Yes you can use generic hose, and I always used a 1" section of tiny copper tubing (same size as the oil pressure tube on the older cars) between the old hose and the new one when making a connection. I would glue them together on top fo the tube so I knew they would not come off.
Willcox
Page 121 in the book will show you the rh vacuum can, this is where the orange hose goes. Page 122 in the book, this is where the green goes, Page 129 item number 3 is where the blue hose goes, Page 130 is whee the black and white hoses go (also pictured in 129). The ac air valve the tan hose goes to is located behind the air box on the driver side. (good luck reaching this one).
Yes you can use generic hose, and I always used a 1" section of tiny copper tubing (same size as the oil pressure tube on the older cars) between the old hose and the new one when making a connection. I would glue them together on top fo the tube so I knew they would not come off.
Willcox
Thanks
Jack
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
