Air flow from vents while rolling but not when stopped. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

meekdog · 03-20-2008, 12:03 PM

When I'm driving I get air flowing through the AC vents even if the heater or AC is switched off. The faster I go, the more air comes in. If I'm stopped no air comes in. If its hot ouside I get hot air. If its cold ouside the air seems to be a little warmer than the outside air. I'm sure its a flap or valve or something but I have no idea where to start without tearing everything apart to find the problem. PS, I also have constant vacuum to the tube which goes to the passenger side kick panel vent. I'm guessing thats not normal either. Thanks for any help you can give, Meekdog.

JimKshortstep4x4 · 03-20-2008, 01:25 PM

I would suggest making sure the air door in the cowl is closed. There is a vacuum operator that closes the door and it may not be working. Check for vacuum at the operator.

Jim

eightbanger · 03-20-2008, 02:26 PM

I've been messing around for a while now with mine so here goes under the dash in the cab where all the heater box stuff is there is one part called the A/Conditioning upper lower diverter box its the one that the S-Plenum is attached to. In this box is a flap that controls whether your air is diverted to the windshield or the floor vent when you select it on the control panel, these fail and the flap stays open letting the air come through your A/C diverter balls and cener vent (this was my problem) I would say your diverter box is the prob as well. The passenger kick panel vent should have vacuum to it keeping it closed and when you select inside air the vent will open, also check the vent door under your cowl look through the slots on the cowl on the passenger side and see if it is open or closed this might have some bearing on your outside air prob. Have a look at5 this thread.
http://67-72chevytrucks.com/vboard/s...d.php?t=283860

There you go Jim helped me.

03-20-2008, 12:03 PM	#1
meekdog Registered User Join Date: Mar 2008 Location: SoCal USA Posts: 5	Air flow from vents while rolling but not when stopped. When I'm driving I get air flowing through the AC vents even if the heater or AC is switched off. The faster I go, the more air comes in. If I'm stopped no air comes in. If its hot ouside I get hot air. If its cold ouside the air seems to be a little warmer than the outside air. I'm sure its a flap or valve or something but I have no idea where to start without tearing everything apart to find the problem. PS, I also have constant vacuum to the tube which goes to the passenger side kick panel vent. I'm guessing thats not normal either. Thanks for any help you can give, Meekdog. __________________ 1972 Chevrolet Cheyenne Super

03-20-2008, 01:25 PM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Air flow from vents while rolling but not when stopped. I would suggest making sure the air door in the cowl is closed. There is a vacuum operator that closes the door and it may not be working. Check for vacuum at the operator. Jim __________________ 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 Last edited by JimKshortstep4x4; 03-20-2008 at 01:30 PM. Reason: Changed wording

03-20-2008, 02:26 PM	#3
eightbanger 454 MAKES IT ROAR Join Date: Jan 2008 Location: Essex, U.K Posts: 2,701	Re: Air flow from vents while rolling but not when stopped. I've been messing around for a while now with mine so here goes under the dash in the cab where all the heater box stuff is there is one part called the A/Conditioning upper lower diverter box its the one that the S-Plenum is attached to. In this box is a flap that controls whether your air is diverted to the windshield or the floor vent when you select it on the control panel, these fail and the flap stays open letting the air come through your A/C diverter balls and cener vent (this was my problem) I would say your diverter box is the prob as well. The passenger kick panel vent should have vacuum to it keeping it closed and when you select inside air the vent will open, also check the vent door under your cowl look through the slots on the cowl on the passenger side and see if it is open or closed this might have some bearing on your outside air prob. Have a look at5 this thread. http://67-72chevytrucks.com/vboard/s...d.php?t=283860 There you go Jim helped me. __________________ 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 02:28 PM.



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