Which is better for AC Recirculate or outside air?

[AKaiser]

betterthanstock hit it square on the head with the oxygen depletion. I always start on MAX/Recirc with the windows cracked an INCH MAX in hot weather (wide open doesn't really flow as well; ask a ventilation specialist), and wide open in cool weather, first because it flows faster, second, because it doesn't cause an overpressure when I close the windows. It makes no difference, on a hot day, whether you use the air from the interior or exterior when you first cool the vehicle down, especially if the windows are down. Once I've got the interior cool, windows go shut, and AC goes to normal outside air.

 

[Bob4x4]

No one brought up the point of people (and animals) using up oxygen. You'll pass out if you leave it on recirculate all the time (first you'll get a headache or nauseated feeling). House AC has by law a small percentage of fresh air brought in all the time (at least in some localities, and newer window AC units have a hole to let in fresh air). I suppose newer cars must have that too, or a lot of people would pass out and wreck (or maybe they do?). I have caught myself feeling drowsy after forgetting it on recirc for half an hour or so.

:-laf:-laf:-laf I don't think so... ... ..... All D/C cars,at least since the 60's have exhaust vents. You can not deplete the 02 in a car,however you can get the humidity so low it will dry you out especialy the eyes. That is what causes the drowsiness.



Bob

 

[JDerrick]

Oo. Take ur pickup down a dirt road for about 20 miles with fine powder dust such as what we have in Northern Nevada. You will see just how air tight your truck isnt..... I have never heard of anyone being oxygen depleated inside of a vehicle unless it was filled with smoke from a fire, or submerged under water. there is enough air passing through especially at highway speeds that it is not an issue. Now on the other hand it is nice to have nice fresh fast moving air while driving, unless you are behind a cattle truck, or drive by a newly flattened skunk or something. Oo.

 

[betterthanstock]

:-laf:-laf:-laf I don't think so... ... ..... All D/C cars,at least since the 60's have exhaust vents. You can not deplete the 02 in a car,however you can get the humidity so low it will dry you out especialy the eyes. That is what causes the drowsiness.



Bob

You are not careful what you are saying. Yes, there are two openings, covered by rubber flaps, on the back of the cab. When the fan draws in outside air, and the windows are closed, the cabin pressure pushes out those flaps, and opens them, letting the air out.



When air is on recirc, a flap closes off (and the question is "how tightly"?) the outside air, so the fan takes inside air and passes it thru the heat exchanger. The exhaust vents stay closed (unless you open a window).



If you can feel the air getting dryer, then you bet there is not enough outside air coming in, and the oxygen will also be getting low. It's just a matter of time, how many people/animals are inside, and how much leakage your cabin has (either deliberate, as in a hole built into the recirculation flap, or other cracks). It will take a while, similar to being in an airplane at high altitude, without a pressurized cabin, or an oxygen mask.



I think some vehicles will automatically switch to outside air after a number of minutes on recirc.

 

[231jasonS]

You are not careful what you are saying. Yes, there are two openings, covered by rubber flaps, on the back of the cab. When the fan draws in outside air, and the windows are closed, the cabin pressure pushes out those flaps, and opens them, letting the air out.



When air is on recirc, a flap closes off (and the question is "how tightly"?) the outside air, so the fan takes inside air and passes it thru the heat exchanger. The exhaust vents stay closed (unless you open a window).



If you can feel the air getting dryer, then you bet there is not enough outside air coming in, and the oxygen will also be getting low. It's just a matter of time, how many people/animals are inside, and how much leakage your cabin has (either deliberate, as in a hole built into the recirculation flap, or other cracks). It will take a while, similar to being in an airplane at high altitude, without a pressurized cabin, or an oxygen mask.



I think some vehicles will automatically switch to outside air after a number of minutes on recirc.

This theory is very funny. The thought of someone passing out due to no Oxygen, you would have to wrap your truck in plastic wrap.



Ive driven for hours with my AC on rec mode with four adults in my truck and no one ever passed out, got dizzy or got a headache.



I dont know which is better for you or your AC system. The answer is as allways ... ... ... ... "it depends".

 

[Bob4x4]

If you can feel the air getting dryer, then you bet there is not enough outside air coming in, and the oxygen will also be getting low. It's just a matter of time, how many people/animals are inside, and how much leakage your cabin has (either deliberate, as in a hole built into the recirculation flap, or other cracks). It will take a while, similar to being in an airplane at high altitude, without a pressurized cabin, or an oxygen mask.



I think some vehicles will automatically switch to outside air after a number of minutes on recirc.

:-laf

Do you have any idea how small an 02 molecule is and how big gaps in a truck are??



Bob

 

[roperteacher]

Your on to something there. . LOLOL I think I can see Daylight in a couple places so I think there is air that can get in there. . LOLOL

 

[BBrodin]

Any ideas why the passenger side air would not be as cold as the drivers side? It was very hot outside and we were using the re-circulation setting.



Is there a filter to clean for the outside air?

 

[scootergmc]

This theory is very funny. The thought of someone passing out due to no Oxygen, you would have to wrap your truck in plastic wrap.



Ive driven for hours with my AC on rec mode with four adults in my truck and no one ever passed out, got dizzy or got a headache.



I dont know which is better for you or your AC system. The answer is as allways ... ... ... ... "it depends".

Funny is a good word. I should be dead. I can't think of all the hours I've driven around with the windows up and NOTHING on, or AC recirc... and I'm here to tell about it.

 

[Bob4x4]

Any ideas why the passenger side air would not be as cold as the drivers side? It was very hot outside and we were using the re-circulation setting.



Is there a filter to clean for the outside air?

Star claims about 12 degree diff side to side is normal And Dodge has never had a cabin filter on a truck... ... ... yet. Genos does sell an add on unit.



Bob

 

[firemansdiesel]

No one brought up the point of people (and animals) using up oxygen. You'll pass out if you leave it on recirculate all the time (first you'll get a headache or nauseated feeling). House AC has by law a small percentage of fresh air brought in all the time (at least in some localities, and newer window AC units have a hole to let in fresh air). I suppose newer cars must have that too, or a lot of people would pass out and wreck (or maybe they do?). I have caught myself feeling drowsy after forgetting it on recirc for half an hour or so.

I fixed that problem. When I think the o2 is low. I light a match and see if it lights. If it does then I got enough o2 to survive the trip.....



:-laf:-laf:-laf:-laf:-laf:-laf:-laf:-laf:-laf:-laf

 

[DPKetchum]

Star says that to get the monkey off their back. 12 degrees is a big differance.

 

[CMusgrove]

It has been in the low hundreds here in Tulsa the past few days and there is a substantial difference (at least to me) in the temperature of the air coming out of the vents when the recirculation mode is on. Last summer my biggest gripe with the truck was the AC but for some reason or another I never ran it with the recirc on. Lately, that button is one of the most pushed buttons on the truck. With the fan on high and the recirc on it will cool the cab even at 100+. I don't buy in to the possible asphyxiation theory of leaving the recirc on. I would not think that automobile manufactures would even have it available if that could happen.

 

[bighammer]

In response to one of the replys I got on my other thread... Which is a better setting for our AC systems?? TO put the dial on RECIRCULATE or the one up from that where it uses outside air??? Would either of these cause more icing up of the system?? I have always used Recirc as I thought it made the AC unit work less?? Just curious! Thanks!:-laf

It all depends on the recent diet of the vehicle's occupants. :-laf


I took my 9 year old and a couple of his friends to a waterpark about an hour away, (I know, I deserve sainthood) and the A/C was blowing thick fog out of the dash. It looked like some kind of scene on a magician or musicain's stage show. (told ya it can be humid up here)

 

[Crunch]

With the fan on high and the recirc on it will cool the cab even at 100+. I don't buy in to the possible asphyxiation theory of leaving the recirc on. I would not think that automobile manufactures would even have it available if that could happen.

Same here. I get a solid 40* when on recirc.



There is no way you can suffocate for lack of air in a vehicle. The cab isn't sealed. If it were, the windshields would pop out on the real hot days as the air expanded. Any danger is going to come from exaust fumes building up in the cab. But DP was right when he said that running on recirc all the time lets germs, snot and everything else you exhale get into the evaporator and vents. I ran on recirc all the time when I first got the truck and after a while you get an funky odor.



I've pretty much come to the conclusion that the AC itself is working fine. The problem is the substandard stuff they replaced our beloved freon with. These trucks have a large cab, and the refrigerant simply isn't up to the task.