77 C3 Vacuum Control
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
77 C3 Vacuum Control
Hi All,
I have posted this in the past. The problem is back. I printed up all of the Wilcox color and B&W diagrams that are online, I pulled my whole dash out and all of the 8 month old vacuum lines.
I re installed and re-checked all vacuum lines to the note from the diagrams.
I had the original and a replacement plastic switch, that I realized after I opened that it is only 2 pieces of plastic held together with a plastic pop clip. I put grease all over it and on the front and back and perimeter.
I took out my Mighty Vac, after all the lines were re done and connected it one line at a time, I checked each vacuum chamber relay one by one and they all work that way.
The 2 vents opened and closed, the center opened and closed (for the A/C), the defrost worked, the hot water control in the engine compartment works and the lower duct worked for the heat. All by Mighty Vac.
I connected the hoses to the 4 inlet lines on the back of the switch. We all know that there are 5 but one is blocked.
When switched to Defrost, Air came out of the top defroster.
When moved to Heat, the hot or cool air came out of the bottom.
When I moved to vent, the outer or firewall vents didn't open but air came out from below
When I went to Max or Normal the large vent wouldn't open but still came out from the lower heat ducts.
If I popped off the main vacuum line and connected it to the Vent chamber or A/C chamber the doors opened.
I also, when the top switch arm is all the way to the left, I am still getting a hissing from the control, no matter how much grease is smeared on the (5) 4 holed vacuum switch or if I try to jiggle or move it. (either one) I still hear an air leak.
I went to a local parts store and replaced the vacuum switch that comes off the intake that has a hole on one side and 2 on the other that only allows air to go one way.
Very frustrating, as everything is correctly done but will not correctly work.
Is there a vacuum psi amount that I should check with a gauge, to make sure I am getting enough vacuum from the black vacuum hose?
Would that do this?
Can someone help me please?
My whole center console and front dash is off the car.
Thanks,
Jack
1977 L-82
1963 SWC
I have posted this in the past. The problem is back. I printed up all of the Wilcox color and B&W diagrams that are online, I pulled my whole dash out and all of the 8 month old vacuum lines.
I re installed and re-checked all vacuum lines to the note from the diagrams.
I had the original and a replacement plastic switch, that I realized after I opened that it is only 2 pieces of plastic held together with a plastic pop clip. I put grease all over it and on the front and back and perimeter.
I took out my Mighty Vac, after all the lines were re done and connected it one line at a time, I checked each vacuum chamber relay one by one and they all work that way.
The 2 vents opened and closed, the center opened and closed (for the A/C), the defrost worked, the hot water control in the engine compartment works and the lower duct worked for the heat. All by Mighty Vac.
I connected the hoses to the 4 inlet lines on the back of the switch. We all know that there are 5 but one is blocked.
When switched to Defrost, Air came out of the top defroster.
When moved to Heat, the hot or cool air came out of the bottom.
When I moved to vent, the outer or firewall vents didn't open but air came out from below
When I went to Max or Normal the large vent wouldn't open but still came out from the lower heat ducts.
If I popped off the main vacuum line and connected it to the Vent chamber or A/C chamber the doors opened.
I also, when the top switch arm is all the way to the left, I am still getting a hissing from the control, no matter how much grease is smeared on the (5) 4 holed vacuum switch or if I try to jiggle or move it. (either one) I still hear an air leak.
I went to a local parts store and replaced the vacuum switch that comes off the intake that has a hole on one side and 2 on the other that only allows air to go one way.
Very frustrating, as everything is correctly done but will not correctly work.
Is there a vacuum psi amount that I should check with a gauge, to make sure I am getting enough vacuum from the black vacuum hose?
Would that do this?
Can someone help me please?
My whole center console and front dash is off the car.
Thanks,
Jack
1977 L-82
1963 SWC
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
Any suggestions?
I have the whole dash and center console out (I had to repair the 2 water leaks that went into the floors. Done)
I just want the control to work.
BTW, I got another bad one way valve, would that do anything?
Thanks
Jack
Last edited by xkeots; Jun 30, 2012 at 02:37 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The Chevrolet Chassis Service Manual has all the necessary diagrams and logic tables to help you diagnose and properly reconnect all that "stuff".
Verbally, I can tell you that the vacuum manifold on the left (selector) thumbwheel has 9 ports and 7 of them have hoses connected; 2 of the ports are for venting and have no hose connections. If you look directly at that manifold from the left side of the car, and view it as a clock dial, the port at 12 o'clock (or 12:30) should be 'open' [no hose]. Then, working around that manifold in a clockwise direction, the hose connections should be tan, blue, green, white, black (this is the incoming vacuum supply line), 'open' [vent #2], pink, and red. If your hoses are connected in the same manner, they should be correct. Of course, the other ends of those hoses need to be connected properly, too. Fig. 50 in the "Air Conditioning" section #15, page 65 is the diagram in the Service Manual used to check all that stuff out.
Verbally, I can tell you that the vacuum manifold on the left (selector) thumbwheel has 9 ports and 7 of them have hoses connected; 2 of the ports are for venting and have no hose connections. If you look directly at that manifold from the left side of the car, and view it as a clock dial, the port at 12 o'clock (or 12:30) should be 'open' [no hose]. Then, working around that manifold in a clockwise direction, the hose connections should be tan, blue, green, white, black (this is the incoming vacuum supply line), 'open' [vent #2], pink, and red. If your hoses are connected in the same manner, they should be correct. Of course, the other ends of those hoses need to be connected properly, too. Fig. 50 in the "Air Conditioning" section #15, page 65 is the diagram in the Service Manual used to check all that stuff out.
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
The Chevrolet Chassis Service Manual has all the necessary diagrams and logic tables to help you diagnose and properly reconnect all that "stuff".
Verbally, I can tell you that the vacuum manifold on the left (selector) thumbwheel has 9 ports and 7 of them have hoses connected; 2 of the ports are for venting and have no hose connections. If you look directly at that manifold from the left side of the car, and view it as a clock dial, the port at 12 o'clock (or 12:30) should be 'open' [no hose]. Then, working around that manifold in a clockwise direction, the hose connections should be tan, blue, green, white, black (this is the incoming vacuum supply line), 'open' [vent #2], pink, and red. If your hoses are connected in the same manner, they should be correct. Of course, the other ends of those hoses need to be connected properly, too. Fig. 50 in the "Air Conditioning" section #15, page 65 is the diagram in the Service Manual used to check all that stuff out.
Verbally, I can tell you that the vacuum manifold on the left (selector) thumbwheel has 9 ports and 7 of them have hoses connected; 2 of the ports are for venting and have no hose connections. If you look directly at that manifold from the left side of the car, and view it as a clock dial, the port at 12 o'clock (or 12:30) should be 'open' [no hose]. Then, working around that manifold in a clockwise direction, the hose connections should be tan, blue, green, white, black (this is the incoming vacuum supply line), 'open' [vent #2], pink, and red. If your hoses are connected in the same manner, they should be correct. Of course, the other ends of those hoses need to be connected properly, too. Fig. 50 in the "Air Conditioning" section #15, page 65 is the diagram in the Service Manual used to check all that stuff out.
Thanks
Jack
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
I have all 3 GM manuals for 77. So much printed material on the car.
C3 Restoration guide, wind and water leak book, A/C repair book, AIM, Electrical service trouble shooting guide (on line from Europe club)
Schematics and more.
I just can't get the switches working right, the parts that are made in China keep on crapping out. All of my vacuum lines are set exact to the color Willcox schematic and the GM green manual, but it still hisses and doesn't work correctly.
Thanks
Jack
77 L-82
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