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Old 12-13-15, 01:49AM   #1
Tonino
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Default AC System Vacuum

Hi,

I have a vacuum routing diagram for my 72 firebird with AC and a "refurbished"
9-port vacuum switch that "kinda" works but not according to the diagram.
I'm also not sure the switch is working properly - its a refurbished salvage
unit. I can get the kick panel door to operate and the AC will also operate the
doors but I'm having trouble with the defrost and bi-level modes. Looking for another switch - preferably NOS, but i'll try another used switch if it holds vacuum on all the active ports according to the diagram. Can anyone give me
any leads? I've got the Pontiac Parts Source book but so far haven't had any
luck. Any help would be appreciated.
Thanks
Tonino
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Old 12-13-15, 12:44PM   #2
Mb125
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Did you test the diaphragm on the doors by running vacuum straight to them first to make sure they work?
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Old 12-13-15, 12:45PM   #3
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Did you test the diaphragm on the bi level doors by running vacuum straight to them first to make sure they work?
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Old 12-13-15, 11:55PM   #4
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Quote:
Originally Posted by Mb125 View Post
Did you test the diaphragm on the doors by running vacuum straight to them first to make sure they work?
Yes I did. Plenty of vacuum to the doors and the diaphragm is new -
it opens and closes as it should although not on the port specified on the
72 diagram which would be port 2. If I put the hose on port 1, it'll work
when I rotate the switch around to it.
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Old 12-13-15, 11:59PM   #5
Tonino
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Quote:
Originally Posted by Mb125 View Post
Did you test the diaphragm on the bi level doors by running vacuum straight to them first to make sure they work?
Now that you mention it, no I didn't but I will tomorrow. I wasn't getting
any vacuum on that port on the switch ergo why I'm suspicious of the switch.
Old Air products has a number of NOS vacuum valves and I'm going to call them
tomorrow. Also have a friend with an interchange manual. Will call him and see if there are any other 9-port switches in my configuration that will interchange.

Thanks for your assistance.

Tonino
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Old 12-14-15, 08:50AM   #6
Tonino
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Although I didn't test the for air coming out of the upper dash vents, I do
remember putting vacuum on the Bi-Level line and the diaphragm held vacuum.
Will re-do it again today and turn the system on to see if air blows through the
bi-level vents. Thanks again.

Tonino
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Old 12-14-15, 12:25PM   #7
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I'll keep my eyes out for a switch
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Old 12-19-15, 05:16PM   #8
Tonino
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Ok, thanks - much appreciated.

Been ailing ergo the delay in the reply

I did do a sanity check and put vacuum right to each
vacuum diaphragm tand with the fan on, they all
worked ok. Air coming out of the defrosters and bi-level.
Heater works too. All I need is a good vacuum switch.

Sent the one I took out of the car to Old Air Products for
a rebuild and also the port assignments according to the
correct 70-73 vacuum flow diagram - asked them to test
each of the assigned ports for vacuum. If my switch is
not set up according to the port assignments then its the
wrong switch and will have to look for another. Should
hear from them early next week. They have a number of
NOS switches, but none with my part number.
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Old 12-21-15, 02:27PM   #9
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Hi All,

For what its worth, after considerable head scratching, pondering, and digging, I
say with a high degree of certainty that the 70-73 firebirds (regardless of model) all use
the same vacuum routing diagram in AC equipped cars. The port assignments on the switch are: 1 - White (AC)
2 - Brown (has a "T" - behind glove box and off "T" brown to air inlet
diaphragm on cowl and orange to kick panel inside/outside air).
3 - Black (engine intake manifold vacuum)
4 - Blue (Defrost diaphragm)
5 - Gray (Evaporator purge diaphragm under the hood on evaporator
housing)
6 - Unused
7 - Yellow (Heat)
8 - Unused
9 - Unused

Still wondering if the ports corresponding to the numbers are to the left of the
numbers or to the right of the numbers. Hmmmmmm.

Hope all this helps someone.

Tonino
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Old 12-21-15, 02:30PM   #10
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Default Vacuum Valve Part Number

Sorry all, forgot to add the part number for the Vacuum valve.

70-73 Pontiac Firebird: 9-port part # 7313414 Group 9.279

Tonino
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