A/C air shut off valve
 

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

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?

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.

Re: A/C air shut off valve
 

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.

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).

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?

Re: A/C air shut off valve
 

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.

Re: A/C air shut off valve
 

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.

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).

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.

Re: A/C air shut off valve
 

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.

Re: A/C air shut off valve
 

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.

Re: A/C air shut off valve
 

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

Re: A/C air shut off valve
 

Try these vendors:

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

http://www.brotherstrucks.com/

Re: A/C air shut off valve
 

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

Re: A/C air shut off valve
 

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.

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

Re: A/C air shut off valve
 

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

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

Re: A/C air shut off valve
 

subscribed

Re: A/C air shut off valve
 

Great info. Thanks!

Re: A/C air shut off valve
 

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

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

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,:chevy:

Re: A/C air shut off valve
 

Max A/C = recirculate.