cab pressure- ac/ heat door vents - The 1947 - Present Chevrolet & GMC Truck Message Board Network

vtwinsport · 12-10-2008, 10:24 AM

Does anyone know if the door louvers at the bottom are there for a reason. I'm wondering about sealing them to keep out the cold/hot and make the cab warmer in winter and ac better in summer.
If the cab is anything like a house, I've heard that there has to be a return air vent (in trucks case, a vent to the outside), to cool or heat properly due to air being forced into room (cab), and if the return (vent) is plugged the room (cab) pressure builds up and the heater/ ac literally stops pushing in any more air.
Any thoughts?
thanks.

vtwinsport · 12-10-2008, 10:32 AM

Follow up question to the one above.;
Does the cab draw air form outside when heating or cooling? Or, does it pull air from within the cab to push over the heater core or ac core?
thanks.

D13 · 12-10-2008, 10:54 AM

They are pressure relief valves.
When you slam your doors they vent the pressure to decrease door closing efforts.

Also they provide flow thru ventilation to prevent CO build up (a federal requirement by the way) and allow air to be displaced by the hot/cold air you are pumping in.

Blocking them will decrease air flow into the cab from the HVAC and will result in decresed and uneven heating / cooling.

The input air comes from outside, at the base of the windshield.

James McClure · 12-10-2008, 11:50 AM

D13 is right 100% with this little added "tweak". IF, a vehicle has A\C, then air can be recirculated without any fresh air from the outside getting in IF, A\C is on and set to recirc. Doesn't matter what temp is set at. IF, controls are set for normal A\C, heat or vent, air will be fresh. Leave door vents alone. The amount of air that gets in there isn't going to effect A\C or heating systems very much. Jim

vtwinsport · 12-10-2008, 12:07 PM

Thanks allot for the info. I figured there would be a good reason for the vents but didn't know what that was. I'll leave em as is.

badblu97 · 12-10-2008, 12:49 PM

OK, so now I have a question. I totally removed all the A/C so I could lay out. Im sure I will install a vintage air or something similar, but really wanted to clean up the doors visually. Anyone see any real problems arising?

**Captkaos** · 12-10-2008, 03:01 PM

Those vents have rubber pieces (or suppose to) that allow internal pressure out but not external pressure in.

*78 Chevyrado* · 12-10-2008, 06:04 PM

With the vents blocked your ears will pop everytime you shut the doors with the windows up.

Plus if you run Max AC all the time, the AC pump will run constantly, wasting gas.

74 C-30 · 12-10-2008, 07:45 PM

i rode in a 88 truck with sealed vents and good weather stripping and he had to roll down the window to shut the door or else it wouldnt shut tight due to air being slammed in

12-10-2008, 10:24 AM	#1
vtwinsport Registered User Join Date: Nov 2008 Location: edmonton, alberta Posts: 293	cab pressure- ac/ heat door vents Does anyone know if the door louvers at the bottom are there for a reason. I'm wondering about sealing them to keep out the cold/hot and make the cab warmer in winter and ac better in summer. If the cab is anything like a house, I've heard that there has to be a return air vent (in trucks case, a vent to the outside), to cool or heat properly due to air being forced into room (cab), and if the return (vent) is plugged the room (cab) pressure builds up and the heater/ ac literally stops pushing in any more air. Any thoughts? thanks. __________________ 76 Silverado, 2wd, long box, 350/th350, 3.42 posi, edelbrock performer 64cc heads, edelbrock 1405, 2101 intake, Hedman Headers, Comp Cam XE262 http://beerbreadbike.wordpress.com/ Last edited by vtwinsport; 12-10-2008 at 07:26 PM.

12-10-2008, 10:32 AM	#2
vtwinsport Registered User Join Date: Nov 2008 Location: edmonton, alberta Posts: 293	Re: cab pressure- ac/ heat door vents Follow up question to the one above.; Does the cab draw air form outside when heating or cooling? Or, does it pull air from within the cab to push over the heater core or ac core? thanks. __________________ 76 Silverado, 2wd, long box, 350/th350, 3.42 posi, edelbrock performer 64cc heads, edelbrock 1405, 2101 intake, Hedman Headers, Comp Cam XE262 http://beerbreadbike.wordpress.com/

12-10-2008, 10:54 AM	#3
D13 Registered User Join Date: Feb 2007 Location: Memphis MI Posts: 1,851	Re: cab pressure- ac/ heat door vents They are pressure relief valves. When you slam your doors they vent the pressure to decrease door closing efforts. Also they provide flow thru ventilation to prevent CO build up (a federal requirement by the way) and allow air to be displaced by the hot/cold air you are pumping in. Blocking them will decrease air flow into the cab from the HVAC and will result in decresed and uneven heating / cooling. The input air comes from outside, at the base of the windshield. __________________ 1987 2 ton 1982 250/TH350 beater in progress Dad's 1981 3/4 L6 3 on tree posi and no options, awaiting restoration or scrapping Plus a mess o' tractors

12-10-2008, 11:50 AM	#4
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: cab pressure- ac/ heat door vents D13 is right 100% with this little added "tweak". IF, a vehicle has A\C, then air can be recirculated without any fresh air from the outside getting in IF, A\C is on and set to recirc. Doesn't matter what temp is set at. IF, controls are set for normal A\C, heat or vent, air will be fresh. Leave door vents alone. The amount of air that gets in there isn't going to effect A\C or heating systems very much. Jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.

12-10-2008, 12:07 PM	#5
vtwinsport Registered User Join Date: Nov 2008 Location: edmonton, alberta Posts: 293	Re: cab pressure- ac/ heat door vents Thanks allot for the info. I figured there would be a good reason for the vents but didn't know what that was. I'll leave em as is. __________________ 76 Silverado, 2wd, long box, 350/th350, 3.42 posi, edelbrock performer 64cc heads, edelbrock 1405, 2101 intake, Hedman Headers, Comp Cam XE262 http://beerbreadbike.wordpress.com/

12-10-2008, 12:49 PM	#6
badblu97 Double 6's Join Date: Oct 2008 Location: Winter Haven, FL Posts: 349	Re: cab pressure- ac/ heat door vents OK, so now I have a question. I totally removed all the A/C so I could lay out. Im sure I will install a vintage air or something similar, but really wanted to clean up the doors visually. Anyone see any real problems arising?

12-10-2008, 03:01 PM	#7
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: cab pressure- ac/ heat door vents Those vents have rubber pieces (or suppose to) that allow internal pressure out but not external pressure in. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

12-10-2008, 06:04 PM	#8
78 Chevyrado Account Suspended Join Date: Dec 2007 Location: Unnapreciative, Trollville Posts: 2,079	Re: cab pressure- ac/ heat door vents With the vents blocked your ears will pop everytime you shut the doors with the windows up. Plus if you run Max AC all the time, the AC pump will run constantly, wasting gas.

12-10-2008, 07:45 PM	#9
74 C-30 Dually Pride Join Date: Jun 2008 Location: NH Posts: 540	Re: cab pressure- ac/ heat door vents i rode in a 88 truck with sealed vents and good weather stripping and he had to roll down the window to shut the door or else it wouldnt shut tight due to air being slammed in __________________ If I have to explain, you wouldn't understand. '74 Chevy C-30 350/4 speed/dually '94 Ford Ranger



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