Heat coming from A/C vents when heater is completely off??

Driver72 · 10-09-2007, 12:29 AM

So I never noticed this with my 335i sedan when I had it last winter, but two days ago while driving home in my 335i Coupe on a cool night in LA, I felt like my cabin was getting a bit warm. Weird considering it was 57 degrees outside.

I cracked my windows a bit to let some cool night air in.

But then I decided to put my hand up by the A/C vents, and sure enough I could feel a slight "breeze" of really warm air coming from the vents.
I looked down at my A/C controls and noticed everything was OFF.
There was not one light lit up on the A/C console.

It was obvious I was getting a bit of heat coming in from the engine, but shouldn't the vents be completely closed when the A/C-Heater is completely off?

Am I missing something or have other people noticed a trickle of hot air coming from their A/C vents when everything is turned off?

Thanks

///Matt · 10-09-2007, 12:36 AM

If your car is not specifically set to recirc, or Auto recirc, it will be in fresh air mode. Air pressure as you drive will force air into the a/c system, and through your vents. I believe the system defaults to heat when it's shut off, so the air is passing through the heater core before it gets to you.

So yes, this is normal. =)

Driver72 · 10-09-2007, 12:42 AM

Ah that's probably it, because I in fact did not have on the recirculate air button.
I'll have to turn that on.

Thanks Matt.

karliejai · 10-09-2007, 03:34 AM

the "rest" button?

Lee Rambler · 10-09-2007, 10:59 AM

yes, seen the same thing on all of my bmw's

Sedan_Clan · 10-09-2007, 12:17 PM

Quote:

Originally Posted by ///Matt

If your car is not specifically set to recirc, or Auto recirc, it will be in fresh air mode. Air pressure as you drive will force air into the a/c system, and through your vents. I believe the system defaults to heat when it's shut off, so the air is passing through the heater core before it gets to you.

So yes, this is normal. =)

+2

To add to this: After awhile, the air coming through the vents will cool off (..providing the ambient air temp is cool), but it does take awhile.

al12345 · 10-09-2007, 12:25 PM

When my climate control is completely off (no recirc is set), all the vents are closed, so there is no passive air flow. To ventilate, I have to turn a fan or a/c on. Is it normal? Is it possible to vent not turning CC on?

DDTAN · 10-09-2007, 12:26 PM

I think you will find that it is due to the design of the car and the ducting, that if you drive the car after it has been warmed up but parked for a short time, the air coming out the vents will be warm. It is for me, and no amount of switching to recirc or not changes it. I believe that it is because the the air ducts are close to the engine compartment, and the air it it get's warmed up. The only way to fix it is to turn on the AC.

rrandyy · 10-09-2007, 12:49 PM

Quote:

Originally Posted by karliejai

the "rest" button?

No, I think the "rest" button is the "residual heat" button

Spool · 10-09-2007, 12:51 PM

I get this too, but the heat is coming from the footwell area, and slightly from the regular vents...it's there, but not noticeable.

And someone my car smells like a baked potato

10-09-2007, 12:29 AM	#1
Driver72 Brigadier General 329 Rep 4,484 Posts Drives: 335i - to new owners now. Join Date: Dec 2006 Location: California iTrader: (0)	Heat coming from A/C vents when heater is completely off?? So I never noticed this with my 335i sedan when I had it last winter, but two days ago while driving home in my 335i Coupe on a cool night in LA, I felt like my cabin was getting a bit warm. Weird considering it was 57 degrees outside. I cracked my windows a bit to let some cool night air in. But then I decided to put my hand up by the A/C vents, and sure enough I could feel a slight "breeze" of really warm air coming from the vents. I looked down at my A/C controls and noticed everything was OFF. There was not one light lit up on the A/C console. It was obvious I was getting a bit of heat coming in from the engine, but shouldn't the vents be completely closed when the A/C-Heater is completely off? Am I missing something or have other people noticed a trickle of hot air coming from their A/C vents when everything is turned off? Thanks
	Appreciate 0 Tweet Quote

10-09-2007, 12:36 AM	#2
///Matt United States Marine 318 Rep 2,748 Posts Drives: 2007 Dodge Ram 1500 Join Date: Jul 2006 Location: Los Angeles iTrader: (8) Garage List 2006 330i [0.00]	If your car is not specifically set to recirc, or Auto recirc, it will be in fresh air mode. Air pressure as you drive will force air into the a/c system, and through your vents. I believe the system defaults to heat when it's shut off, so the air is passing through the heater core before it gets to you. So yes, this is normal. =)
	Appreciate 0 Quote

10-09-2007, 12:42 AM	#3
Driver72 Brigadier General 329 Rep 4,484 Posts Drives: 335i - to new owners now. Join Date: Dec 2006 Location: California iTrader: (0)	Ah that's probably it, because I in fact did not have on the recirculate air button. I'll have to turn that on. Thanks Matt.
	Appreciate 0 Quote

10-09-2007, 03:34 AM	#4
karliejai Da Kid 121 Rep 4,576 Posts Drives: JetBlack e90 335i Join Date: Mar 2007 Location: USA iTrader: (4)	the "rest" button? __________________ MODS: OEM Front Splitter \| ACS Roof Spoiler \| OEM Trunk Spoiler \| Matt Black Front Grill \| Black Shadowline Window Trim \| Painted Front Lower Rod \| Blacklines \| JDM Yellow Fogs \| Custom Silver CF Headlights with LUX 4.0 \| Eisenhaus Sports Exhaust
	Appreciate 0 Quote

10-09-2007, 10:59 AM	#5
Lee Rambler Captain 17 Rep 605 Posts Drives: 07 e92 335 6mt, 04 e53 x5 4.4 Join Date: Mar 2007 Location: PA iTrader: (0)	yes, seen the same thing on all of my bmw's
	Appreciate 0 Quote

10-09-2007, 12:25 PM	#7
al12345 New Member 3 Rep 15 Posts Drives: E92 335i Join Date: Oct 2007 Location: SoCal iTrader: (0)	When my climate control is completely off (no recirc is set), all the vents are closed, so there is no passive air flow. To ventilate, I have to turn a fan or a/c on. Is it normal? Is it possible to vent not turning CC on?
	Appreciate 0 Quote

10-09-2007, 12:26 PM	#8
DDTAN Private First Class 2 Rep 130 Posts Drives: 07 335i E90 ZSP Join Date: Aug 2005 Location: Gig Harbor iTrader: (0)	I think you will find that it is due to the design of the car and the ducting, that if you drive the car after it has been warmed up but parked for a short time, the air coming out the vents will be warm. It is for me, and no amount of switching to recirc or not changes it. I believe that it is because the the air ducts are close to the engine compartment, and the air it it get's warmed up. The only way to fix it is to turn on the AC. __________________ April 07 ED \| E90 335i \| AW \| Beige Dakota \| Poplar \| Step \| Paddles \| ZSP \| SFRS \| CA Redelivered 6/15/07
	Appreciate 0 Quote

10-09-2007, 12:51 PM	#10
Spool ****** 558 Rep 6,169 Posts Drives: A few Join Date: Apr 2007 Location: DC Metro iTrader: (24)	I get this too, but the heat is coming from the footwell area, and slightly from the regular vents...it's there, but not noticeable. And someone my car smells like a baked potato __________________ MKIV 6spd 1000hp Club
	Appreciate 0 Quote