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Discussion Starter #1
Where does the vacuum line connect with the controls on a 78 El Camino? The air conditioning and heat doesn't come through the middle dash vents. With the radio out of it's spot, I thought I should get this fixed.
 

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see if you have vacuum thru the Vac ball then to the control panel,
those lines get brittle and crack/ break..

#1 is the vacuum connection from the Vacuum Ball
#2 is the double acting actuator on the duct for upper defrost, center vent, lower heat..

heatacdashAC Vac.jpg
 

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Discussion Starter #3
Thank you JJ. I appreciate your time and help.
 

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Discussion Starter #4
My problem may be with the lines coming off the vacuum ball under the hood. The problem might be that I didn't get the right line to the right place. The purple line and the orange line rotted out under the hood, so I used black air line to replace them. I ran the line from heater control on the engine to the ball on the fender. I put a T on the first hole of the ball. Then ran a line from the other hole on the ball. Both went down into the cab. I used black, because I couldn't find any lines in color. This is what it looks like. Since I don't remember which line went where, I might try switching the lines.
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The larger fitting on the ball goes to intake manifold vacuum. No "T" involved
 

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Discussion Starter #6
Thank you Neil. This 78 has always had a T with 2 lines going to the cab. How should I accomplish to make a correction?
 

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On mine one line (grey I think) went to the heater valve and the other went to Ball and the bigger line went to the intake at the rear of the carb. The A/C control head would supply the heater valve with vacuum when the heater was not turned on and cut the vacuum to the valve when the heater is turned on. The other line supplies the control head with the vacuum to control the heater valve and the DEF/AIR/Heat valves. I may be way off for yours since the difference in years but I think it's pretty close. I'm goin on memory so be nice, and I can't seem to find a 78 specific heater diagram. Best of luck!

Joe
 

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Discussion Starter #8
Thanks Joe. Mine doesn't hook to the manifold , it hooks to a heater thermostat.
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IMG_20200429_173339407_HDR.jpg
 

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Discussion Starter #9
The connection on the engine may be due to this engine came out of a 73. If the tube is off the thermostat on engine, it runs terrible.
 

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I'm still running on memory and don't have a 78 diagram but the way I see this your control is not getting any vacuum! One of the two lines going to the dash has to be attached to the vacuum source for anything to work. One line needs direct vacuum and one supplies vacuum to the valve. I deleted the ball on mine and have one line to the intake and the other to the heater valve and all works great! I did have to use a by-pass valve instead of a cut-off valve because of the LS water pump but the principal is still the same, prevent hot water from going through the heater core. Hope this helps!


Joe
WIN_20200429_18_48_58_Pro.jpg


Joe
 

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I don't know about a 78, but the T is different from what i'm used to seeing..
usually there are 3 lines outside
1 from the intake manifold for vacuum source, to the ball
2 from the ball to the control panel
3 from the control panel to the heater control valve
 

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I don't know about a 78, but the T is different from what i'm used to seeing..
usually there are 3 lines outside
1 from the intake manifold for vacuum source, to the ball
2 from the ball to the control panel
3 from the control panel to the heater control valve
That says it the way I was trying to say it!

Joe
 

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Discussion Starter #13
The heat thermostat hooks the Valve cover breather cap. So the tube coming from the engine should go to the ball and the other 2 go from the other side of the ball?
 

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The heat thermostat hooks the Valve cover breather cap. So the tube coming from the engine should go to the ball and the other 2 go from the other side of the ball?
Closer, yes the tube from the intake goes to the ball on the larger port, direct, without a T. One line coming from the cowl/dash goes to the other side of the ball and the other line goes to the heater valve/thermostat control that is near your alternator. If that doesn't work, switch the 2 lines coming from the dash and hopefully all will be well!

Joe
 

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Discussion Starter #15
Thanks Joe. The vent by the alternator is where the vacuum is coming from to the ball. So I just changed it so the line from by the alternator is going in the ball by itself and moved the T for the other 2 to the control panel.
 

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Discussion Starter #19
I apologize, I didn't look close enough. The line coming from the heater hose not the breather. That line has been the main line since the year 1996. When the tube comes off the heater thermostat it runs terrible. I guess I'll need to try something different. The ball has 2 holes, one needs to be from a vacuum source. Where does the line from the other side go to?
 

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OK, the ball has 2 holes. One hole goes directly to the intake/carb/vacuum source. The other goes directly to the dash control head for the heat/A/C. The last one will go to the heater control valve/thermostat as you call it. There is no need for the "T" fitting.
 
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