A/C air shut off valve - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Luis_gz06 · 03-20-2008, 02:48 AM

When this valve in the cowl panel closes, does the inside kick panel vent opens? Thanks, Luis.

eightbanger · 03-20-2008, 03:18 AM

Wow spooky! I was going to post this question as well, I noticed this the other day when I fitted my new vacuum valve under the hood and as you say the door under the cowl closes and the vent kick panel opens....it can't be right, anyone know if this is correct?

**john** · 03-20-2008, 03:26 AM

Just a guess, but wouldn't that be changing from outside air to inside air? It has to get air from somewhere.

eightbanger · 03-20-2008, 03:45 AM

Quote:

Originally Posted by john

Just a guess, but wouldn't that be changing from outside air to inside air? It has to get air from somewhere.

Yes the lever on the heater control is set to inside when this happens but when I move the selector lever to outside air the kick panel vent closes again but the vent door under the cowl still remains shut, and all my vacuum valves have been replaced so they are working fine.

JimKshortstep4x4 · 03-20-2008, 03:54 AM

For the coldest AC setting the vent door opens, the water valve closes, and the air door closes on the 70-72 trucks with the two port vacuum switch. Here is a schematic of the two port vacuum switch that I believe you have on your truck. (I can post the three port switch if for some reason your truck has one).

meekdog · 03-20-2008, 04:08 AM

Where exactly is the control head vacuum switch (as shown on daigram) located in the truck? Also would a problem with that switch be responsible for allowing outside air to flow in through the A/C vents when moving, but not when stopped, even if the heater/A/C is switched off?

eightbanger · 03-20-2008, 04:11 AM

Quote:

Originally Posted by meekdog

Where exactly is the control head vacuum switch (as shown on daigram) located in the truck? Also would a problem with that switch be responsible for allowing outside air to flow in through the A/C vents when moving, but not when stopped, even if the heater/A/C is switched off?

On the back of the heater control panel, you have to drop the unit out to get a good look at it but you can see it if you remove the ashtray...not sure on the other question,sorry.

eightbanger · 03-20-2008, 04:14 AM

Quote:

Originally Posted by JimKshortstep4x4

For the coldest AC setting the vent door opens, the water valve closes, and the air door closes on the 70-72 trucks with the two port vacuum switch. Here is a schematic of the two port vacuum switch that I believe you have on your truck. (I can post the three port switch if for some reason your truck has one).

Thanks for that JimKshortstep4x4 I understand it now, couldn't get my head round it before, still unclear though when that door under the cowl opens cause whatever setting I have this thing it's always shut.

JimKshortstep4x4 · 03-20-2008, 04:31 AM

eightbanger,

There should be a spring on the door to open it up when the vacuum is off. Here is a pic of the spring, (the upper end of the spring is hooked to the wrong hole in the picture).

jayharrell · 03-20-2008, 04:58 AM

Think of it like a Max setting, or recirculate. It just shuts off all out side air and recirculates then air in the cab.

eightbanger · 03-20-2008, 05:47 AM

Quote:

Originally Posted by JimKshortstep4x4

eightbanger,

There should be a spring on the door to open it up when the vacuum is off. Here is a pic of the spring, (the upper end of the spring is hooked to the wrong hole in the picture).

Man thats the problem right there I have no such spring I would never have known....Thanks mate another nuisance ticked off the list.

Thanks everyone.

tqlspec · 06-01-2008, 08:23 PM

Quote:

Originally Posted by JimKshortstep4x4

eightbanger,

There should be a spring on the door to open it up when the vacuum is off. Here is a pic of the spring, (the upper end of the spring is hooked to the wrong hole in the picture).

I too am missing this spring. do you know anyone who sells this spring? I'm sure I could use a generic spring if I knew the length and pull strength of the spring. Any idea? I'm considering modifying with a 12V door lock actuator to replace the vacuum.

Photoferg · 08-04-2014, 12:16 PM

Quote:

Originally Posted by eightbanger

On the back of the heater control panel, you have to drop the unit out to get a good look at it but you can see it if you remove the ashtray...not sure on the other question,sorry.

I am looking for a "Control head Vacuum Switch" that is missing on the back of my heater control. Cany anyone help me with a part number or resource to purchase one? Thanks, Bob

**landy** · 08-07-2014, 12:11 AM

Try these vendors:

http://www.lmctruck.com/ICATALOG/CB/t.aspx

http://www.brotherstrucks.com/

picklito · 08-07-2014, 11:14 PM

I don't have that spring, either! NEVER HEARD OF IT!! Thanks so much!

**FirstOwner69** · 08-08-2014, 08:16 AM

Quote:

Originally Posted by tqlspec

I too am missing this spring. do you know anyone who sells this spring? I'm sure I could use a generic spring if I knew the length and pull strength of the spring. Any idea? I'm considering modifying with a 12V door lock actuator to replace the vacuum.

Here's a picture of an original spring. It is very "stout". They are almost always missing due to their location and rust. They are not reproduced as far as I know.

**CUSTOM/10** · 08-08-2014, 09:42 AM

Go to your local hardware store, they usually have an assortment of springs, I found one similar to the one Firstowner posted. Also note the one in the first picture, is hooked to the wrong hole in the cowl. It should be in the hole to the right that's a little further away from the windshield. At least that's what I was told.

Gary

**FirstOwner69** · 08-08-2014, 09:44 AM

Quote:

Originally Posted by CUSTOM/10

Go to your local hardware store, they usually have an assortment of springs, I found one similar to the one Firstowner posted. Also note the one in the first picture, is hooked to the wrong hole in the cowl. It should be in the hole to the right that's a little further away from the windshield. At least that's what I was told.

Gary

I agree. That is the correct hole for the spring.

Bigdav160 · 08-08-2014, 11:07 AM

Thanks for posting the pics. I went and checked and my spring is missing. Off the hardware store I go

WhiteWhale · 08-08-2014, 03:44 PM

subscribed

swclassics · 08-09-2014, 12:32 AM

Great info. Thanks!

El Campo · 08-16-2014, 01:25 PM

I like this thread. It is very informative. Subscribed for future reference

72 K20 · 04-26-2015, 02:11 PM

I learned something new today about the presence of this spring and the fact that I don't have one ! Thank You for the info !!!!
Tom

Andy4639 · 04-26-2015, 08:10 PM

If your not a puriest the best mod you can do is close off that cowl vent completely! Seal it up tight and never close the passenger side kick panel vent again.
I'm not joking either. Your AC will be cooler and you want have all these problems with it anymore.One of the best mods I ever did,

mechanicalman · 04-26-2015, 09:53 PM

Quote:

Originally Posted by Luis_gz06

When this valve in the cowl panel closes, does the inside kick panel vent opens? Thanks, Luis.

Max A/C = recirculate.

03-20-2008, 02:48 AM	#1
Luis_gz06 Senior Member Join Date: Feb 2006 Location: Las Vegas Posts: 1,378	A/C air shut off valve When this valve in the cowl panel closes, does the inside kick panel vent opens? Thanks, Luis. __________________ 1972 Chevrolet Blazer 4x4 (Almost done stay tuned) 1970 Chevrolet Pickup Longhorn CST/20 (SOLD)

03-20-2008, 03:18 AM	#2
eightbanger 454 MAKES IT ROAR Join Date: Jan 2008 Location: Essex, U.K Posts: 2,701	Re: A/C air shut off valve Wow spooky! I was going to post this question as well, I noticed this the other day when I fitted my new vacuum valve under the hood and as you say the door under the cowl closes and the vent kick panel opens....it can't be right, anyone know if this is correct? __________________ Nigel. An American living in a British body. 1971 Chevy Cheyenne 10 454 "In a time of universal deceit, telling the truth becomes a revolutionary act." - George Orwell "When injustice becomes law, resistance becomes duty" - Thomas Jefferson No more pain. 03.12.60 -- 12.28.10 http://www.youtube.com/Eightbanger Last edited by eightbanger; 03-20-2008 at 03:18 AM.

03-20-2008, 03:26 AM	#3
john member #16 Join Date: Dec 1999 Location: Yuba City Ca. Posts: 3,618	Re: A/C air shut off valve Just a guess, but wouldn't that be changing from outside air to inside air? It has to get air from somewhere. __________________ john http://67-72chevytrucks.com/vboard/showgroups.php board vendors http://www.flickr.com/photos/1745471...7602865984234/

03-20-2008, 03:54 AM	#5
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: A/C air shut off valve For the coldest AC setting the vent door opens, the water valve closes, and the air door closes on the 70-72 trucks with the two port vacuum switch. Here is a schematic of the two port vacuum switch that I believe you have on your truck. (I can post the three port switch if for some reason your truck has one). Attached Images __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

03-20-2008, 04:08 AM	#6
meekdog Registered User Join Date: Mar 2008 Location: SoCal USA Posts: 5	Re: A/C air shut off valve Where exactly is the control head vacuum switch (as shown on daigram) located in the truck? Also would a problem with that switch be responsible for allowing outside air to flow in through the A/C vents when moving, but not when stopped, even if the heater/A/C is switched off? __________________ 1972 Chevrolet Cheyenne Super

03-20-2008, 04:31 AM	#9
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: A/C air shut off valve eightbanger, There should be a spring on the door to open it up when the vacuum is off. Here is a pic of the spring, (the upper end of the spring is hooked to the wrong hole in the picture). Attached Images __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

03-20-2008, 04:58 AM	#10
jayharrell Gettin By on Gettin By Join Date: Jan 2008 Location: Cedar Creek, Tx Posts: 1,033	Re: A/C air shut off valve Think of it like a Max setting, or recirculate. It just shuts off all out side air and recirculates then air in the cab.

08-07-2014, 12:11 AM	#14
landy Senior Member Join Date: Jun 2000 Location: alb, nm Posts: 413	Re: A/C air shut off valve Try these vendors: http://www.lmctruck.com/ICATALOG/CB/t.aspx http://www.brotherstrucks.com/

08-07-2014, 11:14 PM	#15
picklito Registered User Join Date: Sep 2013 Location: Vacaville CA Posts: 490	Re: A/C air shut off valve I don't have that spring, either! NEVER HEARD OF IT!! Thanks so much!

08-08-2014, 09:42 AM	#17
CUSTOM/10 Senior Member Join Date: May 2003 Location: Sandown, NH Posts: 2,850	Re: A/C air shut off valve Go to your local hardware store, they usually have an assortment of springs, I found one similar to the one Firstowner posted. Also note the one in the first picture, is hooked to the wrong hole in the cowl. It should be in the hole to the right that's a little further away from the windshield. At least that's what I was told. Gary Attached Images __________________ Gary 72 SWB 4x4 My 72 SWB Build http://67-72chevytrucks.com/vboard/s...d.php?t=259859

08-08-2014, 11:07 AM	#19
Bigdav160 Registered User Join Date: Apr 2011 Location: Klein Texas Posts: 3,852	Re: A/C air shut off valve Thanks for posting the pics. I went and checked and my spring is missing. Off the hardware store I go __________________ My Classics: '72 K20 Suburban + '65 Dodge Town Wagon '72 Corvette Roadster +'67 Corvette Roadster '73 Z-28 Camaro '63 Ford SWB Uni Pickup '50 Ford Coupe

08-08-2014, 03:44 PM	#20
WhiteWhale Registered User Join Date: Apr 2014 Location: Southern California Posts: 200	Re: A/C air shut off valve subscribed

08-09-2014, 12:32 AM	#21
swclassics Registered User Join Date: Aug 2011 Location: Queen Creek, AZ Posts: 39	Re: A/C air shut off valve Great info. Thanks!

08-16-2014, 01:25 PM	#22
El Campo Registered User Join Date: Jul 2011 Location: El Campo, Tx Posts: 1,246	Re: A/C air shut off valve I like this thread. It is very informative. Subscribed for future reference __________________ 72 Chevy blue LWB, 99% original Oklahoma truck, 28,000 miles 72 Chevy SWB: http://67-72chevytrucks.com/vboard/s...d.php?t=486626 (Attempt/Mistake #2) 2003 Harley Davidson Dyna Superglide with 2007 Street Bob front end 2000 Ford F350 Powerstroke 4WD CCLB, 310,000 miles running great (STOLEN St. Patricks Day 2014 AND NEVER RECOVERED) 2002 Ford F250 Powerstroke 4WD CCLB (To replace stolen one) Hook em Horns!!!

04-26-2015, 02:11 PM	#23
72 K20 Registered User Join Date: Mar 2011 Location: Brandon,Iowa Posts: 391	Re: A/C air shut off valve I learned something new today about the presence of this spring and the fact that I don't have one ! Thank You for the info !!!! Tom



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04-26-2015, 08:10 PM	#24
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: A/C air shut off valve If your not a puriest the best mod you can do is close off that cowl vent completely! Seal it up tight and never close the passenger side kick panel vent again. I'm not joking either. Your AC will be cooler and you want have all these problems with it anymore.One of the best mods I ever did, __________________ 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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