"Dual" dual-zone air con...

[Roadhouse]

Hey all.

Got my 2004 4.8is with the dual zone a/c. Pretty straightforward - set the temp to the desired degrees and away we go. Or so I thought...

Question is, what is the point of setting the temps to the desired figure (say 22 degs C) if the scrolling knob between the vents towards the centre-top of the dashboard allows you to pump in hot or cold air? Perhaps it's a convenience feature so upper body air temp is controlled by the knob. Not very convenient as I have to keep adjusting it...

If I just wanted to control my a/c via selecting an actual temp, what position should the scrollable knob be in??

Has me a bit baffled - what do others do?

[SlickGT1]

It is a bmw thing. I actually find it great. I set it a bit cool, so that I don't fry while my baby and CEO are enjoying the warmth.

I can't wait for Qsilver to post up some technical operations of the center vent. So, subscribing and waiting for him to see this.

[Roadhouse]

Originally Posted by SlickGT1

It is a bmw thing. I actually find it great. I set it a bit cool, so that I don't fry while my baby and CEO are enjoying the warmth.

Slick - I too prefer the cooler air, but if the CEO is in the front passenger seat, and if you toggle the centre knob to blow cool air, doesn't she get it also? I thought that this knob set the air flow temp across the top of the dash for both sides of the car, and that you can only change the driver/passenger temps independently via the temp controls? Maybe I have misunderstood your point in your post (entirely possible!)?

Have the same issue for the back vents - a scrollable knob there controls temp of the only (visible) vents in the back. If it has been changed to blow the coldest air due to a hot day, and then I forget to change it next day when it is maybe a cool day, my poor bubba and/or dog in the back freeze their collective asses off whilst we in the front are comfortable (subject to my first post!). Maybe solution for back is set to neutral - neither hot nor cold, and let the climate control take care of temp? Wouldn't work for front as I want cold air on a hot day, hot air on a cold day...

Life is full of compromises and challenges isn't it!!

Anyway, be interested to see others opinions.

[JCL]

This is a standard frustration point with new BMW owners, and some older BMW owners.

First, set the thumb wheel to the centre position, no red or blue dots.

Now the temperature setting on the HVAC will work just fine, and hold a different temperature left or right. Use fully automatic for the vents to be blended by the system automatically, or select one or more vent priorities (def/centre/floor) if you like, still using automatic fan control.

Understand that the centre vent control (thumb wheel) is not an absolute temperature control, it is an offset control. The three dots (red or blue) correspond to a 1, 2, or 3 degree offset from your automatic setting. That mixing only applies to the centre vents, it doesn't affect the outer face level vents.

As an example (using Celcius), I set the left to 19, the right to 20, and the offset to one blue dot, meaning that I get slightly cooler fresh air at face level, which is great for staying alert on a long drive.

The problem happens when people dial the thumbwheel all the way hot or cold, at which point it ends up fighting the automatic control at some settings. The system then can't deal with extremes of cooling the lower level of the cabin and heating the upper level, or vice versa, and resolve what you actually wanted in the first place.

So, leave the thumbwheel in the centre, and resist the urge to play with it for a few days. Do not ever consider it a temperature setting. But once you know what you want the main cabin temperature held at, use it judiciously to adjust for cooler or warmer air on the face vents, depending on your preference. One or two dots is usually plenty. And if the driver or passenger want different results from that centre vent stack, they can be independently shut off, just relying on the outer face level vents.

I had my system adjusted so that I kept the same temperature setting left and right all year, and adjusted the vents from one dot to two, and back, spring and fall. It worked perfectly.

[Qsilver7]

Originally Posted by SlickGT1

...I can't wait for Qsilver to post up some technical operations of the center vent. So, subscribing and waiting for him to see this.

OMG...I guess the bloom is off the rose already...almost two months in...and everyone already has my number.

Originally Posted by Roadhouse

Question is, what is the point of setting the temps to the desired figure (say 22 degs C) if the scrolling knob between the vents towards the centre-top of the dashboard allows you to pump in hot or cold air? Perhaps it's a convenience feature so upper body air temp is controlled by the knob. Not very convenient as I have to keep adjusting it...

If I just wanted to control my a/c via selecting an actual temp, what position should the scrollable knob be in??

Has me a bit baffled

Well...if you want to go with the selected temp...with no other adjustments...then keep the stratified air dial located on the dash's center vent at the neutral mark. I'm so used to this stratified air dial (#3 in the image below) that I really don't pay that much attention to them any longer. Hopefully there's a small white mark on the dial that separates the blue from the red (at least on my other BMWs it's been that way)

EDIT: You can also turn the dash vents off (dial #1)...so if you want warmer or cooler air blowing at you while driving, the front passenger can turn the dash vents off that blow on them, or move the louver (#2) to blow away from them...allowing them to keep the temp setting they've selected that will blow from the floor or defrost vent.

As Slick mentioned in his reply...this air stratification has been used by BMW for decades. I can remember the 1979 e21 3 series a friend of mine owned had this stratified air dial.

The purpose of this system back then before air conditioning or the ability to "temper" the air warmer/cooler...the dial allowed the driver or passengers to blend in fresh air (front dash & at rear of the center console). For instance, if you are driving long distance, the driver can "temper" the air from the dash vents to allow cooler air to blow into their face to keep them alert...while the passengers can remain warm and toasty as the sleep etc.

The same applies to the rear passengers...having an air stratification dial...if they are on the sunny side of the car, they can use the air vent at the rear of the center console to bring in cooler fresh air without having to ask the driver to change the HVAC system for the entire car.

You can see in some of the old diagrams from past BMW models how this stratified air adjustment allows passengers to "temper" the air that blows into their section of the car by blending fresh or cooled air:

Starting in the mid 90s with the e38...BMW upgraded the HVAC system where you could now not only get fresh/cooled air thru the stratified air vents...but you could now temper the air warmer/cooler:

Again, the stratified air dial gives the driver & passengers an opportunity to make small adjustments to make their journey more comfortable, without having the driver change the settings for the entire car. As with many things...the more choices you allow, the more complicated things can become. If you want to set a temp (and forget it)...then set everything to a neutral setting (again, the dial should have a white mark indicating this?)...and the same goes for the rear passengers. You may want to check how that vent at the rear of the center console is set if you've had passengers back there. They may have it adjusted to a summer setting...which may not be conducive to rear passengers during the winter months (or vice versa).

[Roadhouse]

Thanks for the replies - very informative.

[SlickGT1]

Originally Posted by Qsilver7

OMG...I guess the bloom is off the rose already...almost two months in...and everyone already has my number.



Well...if you want to go with the selected temp...with no other adjustments...then keep the stratified air dial located on the dash's center vent at the neutral mark. I'm so used to this stratified air dial (#3 in the image below) that I really don't pay that much attention to them any longer. Hopefully there's a small white mark on the dial that separates the blue from the red (at least on my other BMWs it's been that way)

EDIT: You can also turn the dash vents off (dial #1)...so if you want warmer or cooler air blowing at you while driving, the front passenger can turn the dash vents off that blow on them, or move the louver (#2) to blow away from them...allowing them to keep the temp setting they've selected that will blow from the floor or defrost vent.

As Slick mentioned in his reply...this air stratification has been used by BMW for decades. I can remember the 1979 e21 3 series a friend of mine owned had this stratified air dial.

The purpose of this system back then before air conditioning or the ability to "temper" the air warmer/cooler...the dial allowed the driver or passengers to blend in fresh air (front dash & at rear of the center console). For instance, if you are driving long distance, the driver can "temper" the air from the dash vents to allow cooler air to blow into their face to keep them alert...while the passengers can remain warm and toasty as the sleep etc.

The same applies to the rear passengers...having an air stratification dial...if they are on the sunny side of the car, they can use the air vent at the rear of the center console to bring in cooler fresh air without having to ask the driver to change the HVAC system for the entire car.

You can see in some of the old diagrams from past BMW models how this stratified air adjustment allows passengers to "temper" the air that blows into their section of the car by blending fresh or cooled air:

Starting in the mid 90s with the e38...BMW upgraded the HVAC system where you could now not only get fresh/cooled air thru the stratified air vents...but you could now temper the air warmer/cooler:

Again, the stratified air dial gives the driver & passengers an opportunity to make small adjustments to make their journey more comfortable, without having the driver change the settings for the entire car. As with many things...the more choices you allow, the more complicated things can become. If you want to set a temp (and forget it)...then set everything to a neutral setting (again, the dial should have a white mark indicating this?)...and the same goes for the rear passengers. You may want to check how that vent at the rear of the center console is set if you've had passengers back there. They may have it adjusted to a summer setting...which may not be conducive to rear passengers during the winter months (or vice versa).

Yup, I got your number. Thanks for this. Others have asked me what that is, and I always found it a bit tough to reason why BMW has this in every car. This is great.

[BuzZLtYr]

great info!! thanks for clearing things up. i always had a little trouble w/ that dial.

[X5SND]

Good god man! You are a wealth of knowledge!