Air from A/C Vents When System is Off

[tjc78]

It was a nice 54 degree morning. On my way to work with the windows up I needed no a/c or heat, however the system was blowing warm air out of the upper (panel) vents. I switched it to the floor vents but still was warm and then the outer vents were blowing warm air as well. I turned the system on and dialed it down to "low" and then shut it off. The car still blew warm air into the cabin. My 99 S-10 does this as well (many GM cars do), but if you turn the temp dial all the way to cold it's fine. Has anyone else noticed this? Is there a setting I missed? I don't mind the air flow just don't want warm air when its not cold out.

 

[Sayantsi]

Afaik since the 90s, all passenger cars have to have a passive airflow system to reduce the possibility of CO poisoning. The car will vent itself at speed even if you have everything off and the system on recirculate (not sure about this last part). Air travels through the cabin and trunk. I'd guess the air temp coming in is dictated by the ambient temps plus engine heat.

 

[tjc78]

I know that the air blowing through is normal, what I found funny was that it was warm and it really shouldn't have been. Maybe I am nitpciking. You mentioned the recirc button, I am going to try pushing that button on the drive tomorrow morning to see if that stops the airflow.

 

[dataguy]

Actually, there's a warning in the owner's manual about leaving recirc on, including when sleeping in the car. I took that to mean that there's the possibility of either CO poisoning or lack of oxygen. Given how noise insulated the car is, it seems to be fairly airtight.

If one of the points of recirc is to keep smog out of the cabin, having external airflow into the cabin seems to defeat the purpose.

As for the warm air, if the climate control temperature is higher than the ambient temp (as indicated on the display), it will blow warm air to try to raise the temp to the CC setting. Doesn't really explain why it would do that on Low though.

 

[muisui]

this happens to all my cars in the US acrossed 4 brands.
Toyota, audi, bmw and mini

 

[tjc78]

My Avalon did it too.... however it was never warm air always ambient temp.

 

[mikec]

Just about every car lets fresh air "ram" into the cabin even with the AC/heater/fan OFF. In RECIRCULATE mode the "ram air" passage is blocked and you feel no airflow. Some vehicles will still try to heat the air if the temp controls are set to higher than whatever the cabin temp is (my Starion is that way, it's very annoying. OFF should be OFF!!!) Others, when OFF, just pass the air through and ignore temps completely - like my uncomputerized Corolla.

On some vehicles that really understand OFF means OFF - and don't try to heat the air to match the temp controls - you may still feel warmer air from the vents. Such cars have the air ducting run right under the dash top typically, or along the fenders... so sunlight bakes the dash/fenders and leads to hot ductwork. Several Hondas (Accords and Preludes if I remember correctly) made this goof. It took several minutes of A/C operation to chill those ducts; the airflow through the vents was quite warm for a while.

mike c.

 

[acey]

Sure it wasn't the heated seats? I was hearing a noise and thought the fan was too loud, when I realized I had the seat AC on, and not the fan at all.

 

[tjc78]

All is good, like others suggested I just pushed the "recirc" button and all air stops flowing when the system is off. Thanks!

 

[ilovemygenesis]

Given how noise insulated the car is, it seems to be fairly airtight.


I would disagree with that statement, i hear more outside noise when i drive then i expect to hear.

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[dataguy]

Given how noise insulated the car is, it seems to be fairly airtight.


I would disagree with that statement, i hear more outside noise when i drive then i expect to hear.

Compared to what? What sort of noise are you hearing that you don't expect to hear? There's a lot of road vibration that's transferred acoustically given the suspension tuning and the performance tires, but from an insulation from ambient and engine compartment noise perspective, it's definitely one of the quietest in the price segment. Look at the door seals, they're better insulated than my house. The glass is also laminated, which cuts down on noise transmission.

"In road tests, our editors have found that this decadent four-door is Lexus-quiet on the highway..." -- Edmunds.com

Edmunds full test sound measurements (V6):
Db @ Idle: 39.6
Db @ Full Throttle: 70.8
Db @ 70 mph Cruise: 63.5

Car & Driver track test sound measurements (V8):
Db @ Idle: 39 avg
Db @ Full Throttle: 74 avg
Db @ 70 mph Cruise: 67 avg

"Inside it's as quiet as Lexus GS..." -- U.S. News & World Report

If it's not quiet enough, then you can add additional body insulation: http://www.koreanautoimports.com/store/product_info.php?cPath=31_237_239&products_id=1632

 

[acey]

Sure it wasn't the heated seats? I was hearing a noise and thought the fan was too loud, when I realized I had the seat AC on, and not the fan at all.

That was my suggestion until I realized that I misspoke. When I had the seat AC on, it is truly silent.

But I had all the dashboard vents inadvertently in their closed positions except the far left drivers side one, and I was hearing all the forced air coming out of that one open vent. When I reopened the vent just to the right of the steering wheel, all the fan noise was rendered almost imperceptible.

As far as hearing road noise...this is the quietest car I've ever been in. Even on freeway, the enjoyment of the sound system is remarkable!!!

 

[ilovemygenesis]

Compared to what? What sort of noise are you hearing that you don't expect to hear? There's a lot of road vibration that's transferred acoustically given the suspension tuning and the performance tires, but from an insulation from ambient and engine compartment noise perspective, it's definitely one of the quietest in the price segment. Look at the door seals, they're better insulated than my house. The glass is also laminated, which cuts down on noise transmission.

"In road tests, our editors have found that this decadent four-door is Lexus-quiet on the highway..." -- Edmunds.com

Edmunds full test sound measurements (V6):
Db @ Idle: 39.6
Db @ Full Throttle: 70.8
Db @ 70 mph Cruise: 63.5

Car & Driver track test sound measurements (V8):
Db @ Idle: 39 avg
Db @ Full Throttle: 74 avg
Db @ 70 mph Cruise: 67 avg

"Inside it's as quiet as Lexus GS..." -- U.S. News & World Report

If it's not quiet enough, then you can add additional body insulation: http://www.koreanautoimports.com/store/product_info.php?cPath=31_237_239&products_id=1632

With the radio off and all the windows up it sounds like one of my windows are open a bit. Regardless of if my sunroof cover is open or not, it's not a loud rushing sound but it's noticeable. When i go for my next service appt i'll have them look at it while they put in my speaker trunk cover. My Acura 3.5RL was like a bubble, i didn't hear anything from outside (well not anything but darn close). I should have told the salesman to shut up when i did my test drive,lol it's not a deal breaker but sometime when i drive i like it to be quiet and peaceful and i can't do that now, ohhh well.