Cowl inlet valve on A/C trucks - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chewed 71'er · 09-29-2002, 02:17 PM

I recently replaced the cowl (plenum) air inlet valve in my 71. It fits good and closes nicely, but will not open on its own. Removed vacuum line from diaphragm, but had no affect. Is the diaphragm return spring weak? Is there an external return spring missing? This is the first time I've dealt with this setup, looking for ideas.

1-PU70 · 09-29-2002, 05:25 PM

I think it opens WITH vacume.

**smitty62** · 09-29-2002, 06:05 PM

closes with vacuum--opens with an external spring mounted on the cowl--look for a small spring hole in the cowl louvers.

1-PU70 · 09-30-2002, 12:06 PM

Thats it closed with vacume. Sorry

chewed 71'er · 09-30-2002, 08:39 PM

Thanks, gents. I think I see how this system operates. Now got to make it functional!

09-29-2002, 02:17 PM	#1
chewed 71'er Registered User Join Date: Mar 2002 Location: KC, NW Missouri Posts: 144	Cowl inlet valve on A/C trucks I recently replaced the cowl (plenum) air inlet valve in my 71. It fits good and closes nicely, but will not open on its own. Removed vacuum line from diaphragm, but had no affect. Is the diaphragm return spring weak? Is there an external return spring missing? This is the first time I've dealt with this setup, looking for ideas.

09-29-2002, 05:25 PM	#2
1-PU70 Registered User Join Date: Apr 2000 Location: Bradenton, FL Posts: 1,036	I think it opens WITH vacume. __________________ 1970 CST/10 402,700R4,3:73 posi,AC,PS,PB,TLT,PW,Buckets with heaters

09-29-2002, 06:05 PM	#3
smitty62 Registered User Join Date: May 2002 Location: North Carolina Posts: 1,234	closes with vacuum--opens with an external spring mounted on the cowl--look for a small spring hole in the cowl louvers. __________________ Stepsides look like real trucks! Smitty

09-30-2002, 12:06 PM	#4
1-PU70 Registered User Join Date: Apr 2000 Location: Bradenton, FL Posts: 1,036	Thats it closed with vacume. Sorry __________________ 1970 CST/10 402,700R4,3:73 posi,AC,PS,PB,TLT,PW,Buckets with heaters

09-30-2002, 08:39 PM	#5
chewed 71'er Registered User Join Date: Mar 2002 Location: KC, NW Missouri Posts: 144	Thanks, gents. I think I see how this system operates. Now got to make it functional!



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