Vacuum for ac/heater blend doors

DoubleL

DoubleL

Not-quite-so-new-guy
Oct 4, 2018
5
3
3
#1
I recently had 5.3 LS swapped into my 1985 El Camino. Had new AC compressor installed also. AC blows cold but only through the defrost vents. I found that the vacuum is not connected at the firewall under the hood. Can anyone tell me where and how to get the vacuum connected to get the blend doors to operate. I also noticed that the heater control valve probably should have vacuum to it also, correct? Thanks in advance.
 
fleming442

fleming442

Comic Book Super Hero
Dec 26, 2013
4,562
4,555
113
#2
Purple vacuum line controls the vents- hook to manifold vacuum.
Gray/white line goes to the heater control valve on the small heater core line- shuts off flow to heater core during A/C operation.

The rubber selector in the vent control is notorious for selection problems. It is held by a small plastic rivet that deteriorates and breaks. It can be fixed by replacing with a small screw.
 
MrSony

MrSony

Comic Book Super Hero
Nov 15, 2014
4,265
2,586
113
Des Moines, Iowa
#3
You need a 2 port vacuum reservoir. purple in one nipple vaacuum line from the other to manifold vacuum. plus or minus a check valve. white/grey line goes to the heater shutofff valve to shut off coolant flow from the heater core. idk if that will work anymore with your setup.
 
fleming442

fleming442

Comic Book Super Hero
Dec 26, 2013
4,562
4,555
113
#4
I added the reserve ball to mine (1 port, teed into the purple between the engine and firewall), and didn't notice any difference; the vents worked either way.
 
DoubleL

DoubleL

Not-quite-so-new-guy
Oct 4, 2018
5
3
3
#5
Do either of you have a picture available?
 

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