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#1 |
Registered User
Join Date: Jun 2007
Location: orlando, fl
Posts: 19
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Vacuum switch on the A/C control
I have two A/C control units. One has 3 vacuum switches and the other has 2. Other than that they look identical. What’s the difference? The truck had the one with 2 vacuum switches. Ohhh yeah ist for my 72 with factory air.
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--your mom is on my buddy list-- Last edited by badmilk; 06-22-2007 at 01:02 PM. |
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#2 |
Zappaphile!
Join Date: Apr 2007
Location: Los Banos, California
Posts: 228
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Re: Vacuum switch on the A/C control
been down this road..
See: http://67-72chevytrucks.com/vboard/s...d.php?t=225592 And.. http://67-72chevytrucks.com/vboard/s...controls+lines Goodluck
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1969 C20 LWB Camper Special - The Beater.. 1998 Cheyenne V6 - 4/6 Drop - For The Son |
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#3 |
Senior Member
Join Date: Nov 2005
Location: northwestern wi
Posts: 2,111
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Re: Vacuum switch on the A/C control
it appears the third port goes to the water controal valve.that one was plugged on mine. i'm just now trying to sort this out two
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common sense isn't so common anymore |
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#4 |
Registered User
Join Date: Jun 2007
Location: orlando, fl
Posts: 19
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Re: Vacuum switch on the A/C control
i capped the port on the left and it seems to be working.
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--your mom is on my buddy list-- |
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#5 | |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Vacuum switch on the A/C control
Quote:
I'm also in the position of having a 3-port repop control. They're numbered 1-2-3 and I've searched a lot on the board... no posts seem to list what's what. I've seen the shop manual drawing, but it doesn't indicate which port is actually which. Any help?
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#6 |
Moderator
![]() Join Date: May 2007
Location: Southern Cal
Posts: 20,006
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Re: Vacuum switch on the A/C control
He is correct. Look at the second diagram in post number 5: http://67-72chevytrucks.com/vboard/s...controls+lines
The third port goes directly to the water control valve. You can also just cap it off and t off of the other line as the two port setup does.
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1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man |
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#7 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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It depends on which manual you look at. The 71 manual is this way.
![]() ![]() The 69 shows it this way. ![]() ![]()
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#8 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Vacuum switch on the A/C control
Only problem is that I'm using a 3-port replacement control in a '70 where I'm going to use the proper '70 routing (heater valve off a T under the hood).
I just don't know which of the 3 ports correspond to the older 2-port units.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#9 |
Moderator
![]() Join Date: May 2007
Location: Southern Cal
Posts: 20,006
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Re: Vacuum switch on the A/C control
Start capping them off one at a time and see which two you need to use to make it function properly.
__________________
1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man |
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#10 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Vacuum switch on the A/C control
What's properly in this case? In which switch position should it pass vacuum and which should be closed?
I may be able to find the old one to check it, but just in case...
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#11 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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Easy man look at the 71 picture with three lines. The bottom line is for the water shut off. Cap this line. Then tee the line out of the center one for the other vacuum operated valves. The top is for the source of vacuum.
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#12 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Vacuum switch on the A/C control
Thanks! In the picture you're referring to which do you consider top and which is bottom? I assume you mean that the "missing" one is the water one. Which is weird since that means the ports 2 and 3 do the same thing - so why they'd add complexity to the switch to remove a plastic vacuum tee I don't know. It even requires more hose and additional run through the firewall. I wonder why they changed it?
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#13 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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The reason for I'm not sure of other than if you get a cut in the line for all three vacuum operated valves. With 2 seperate lines at lest you have a vacuum source. Not really sure though.
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__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#14 |
Moderator
![]() Join Date: May 2007
Location: Southern Cal
Posts: 20,006
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Re: Vacuum switch on the A/C control
With the A/C on, the inside passenger vent door (recirculating air) should be open (vacuum applied) the cowl vent door (fresh air) should be closed (vacuum applied), and water valve closed (vacuum applied)
You will just have to use a trial and error method as to which switches do what. The above diagrams have all the info needed.
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1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man |
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#15 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Vacuum switch on the A/C control
So the problem I'm now seeing is that the switch really doesn't hold vacuum worth a crap. Nor does my old original. When I connect a vacuum pump (brake bleeder thing with a gauge) I can pump up vacuum but it bleeds off in a jerky fashion about as fast as I can pump it.
If I connect the vacuum pump directly to the vent solenoid, it'll hold vacuum for hours, so its not the pump or the solenoid. I guess if you're talking about a 400cid engine rather than a hand pump maybe it doesn't matter, but I still find it odd. Seems like a vacuum leak and I don't want it affect the idle and so on. Am I the first to test the switch or has anyone had a similar (or different) experience with them? Thanks! Dave
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#16 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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How did you test it? Did you cap each line off other than the one you pulled vacum on? If so did you check the caps to see if they where the leaks. if so I would buy a new one.
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__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#17 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
|
Re: Vacuum switch on the A/C control
Buy a new one what? Both the old and the new do the same thing.
Yes, I capped them all but one at a time. Hey, I always appreciate your input, but have you considered not making your posts bold red and shortening your manifesto of a signature? It makes your answers hard to read :-)
__________________
1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#18 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
|
Re: Vacuum switch on the A/C control
According to the 70 manual it follows the 71 method of a line for the heater switch all the way to the vacuum switch. Which is weird because my truck is a 70 but came with the two-port.
__________________
1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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