# Climate control, AC & the mysterious center vent wheel thing?



## Moderato (Nov 24, 2003)

First let me say that I love my new E46 and this post is in no way a complaint about the climate control system but rather an opportunity for some of you to comment on my obsevations and a request for help in better understanding how to operate the system. I've also already done a search and read many threads about the climate control in the E46, but I'm still confused about some things.

First off that center vent wheel thing has me confused. I understand how it works and why some people feel it to be a good feature, but what I'm asking basically is what is the proper way to use it in conjunction with the AUTO climate control system? Should you just put it on the middle white dash setting? 

Why it doesn't make sense to me is because of this: my understanding of how a climate control system should work is like this: you set it for 65 (let say the outside air temp is 36), the system does whatever it takes to get the cabin temperature to 65 degrees and then maintains that temperature. This means it will blow somewhat hot air and when the temp reaches 65 it will slow the velocity of the airflow and moderate the temperature of the air as well in order to comfortably maintain 65 degrees. Am I wrong here?

Therefore if you have it set to AUTO at 65 degrees and you have the center dash vent thing adjusted to full cool or mostly cool, what is the point of that? OK, so the middle airflow won't be as hot as the foot & windshield vents but won't the AUTO program still try to maintain 65 despite the cooler mid level air flow and make the foot and windshield vents blow hotter then would normally be necessary and roast your feet and your forehead in an effort to compensate for the cooler air temp of the center vents? So what you have to do is try to get the center vents to blow air of 65 degrees with the center control vent dial in order to aid the AUTO system to get the cabin temp to what you have set. Only problem is that it's hard to tell exactly what 65 degree air blowing out of the center vents feels like with your hand for a thermometer. 

Which leads me to another point. The outside air temp hasn't gotten hotter then say 59 degrees here in the North East so I've been using the AUTO mode but deactivating the AC. Does this confuse the AUTO climate? If I have the AC activated with an outside air temp of 36 degrees and the AUTO set to 65 will having the AC on make the system more effecient and operate better even though one would think that it wouldn't be necessary when the outside air temp is 36 degrees? (Let's just forget about the humidity factor for now). If the outside air temp is below 50 degrees shouldn't the AC not come on automatically since the 50 degree outside air should be cold enough to get the cabin temp to 59 degrees or more without the aid of the AC compressor? (again lets just forget about humidity control for now. If you felt the air was too humid you could then press the AC button and "tell" the climate control system that you want the air to be de-humidified as well)

If I go to manual control I can have complete control over the system, well not exactly but I can get the center vents to exactly the temp I want if I utilize the center vent knob and set the digital temp buttons to a rough estimate of the temp I want the vent air to be. This was fine until I tried to also activate the windshield vents at the same time and the air that blew out of those felt like it was 30 degrees hotter then the air I had coming out of the center vents, and it was the same if I activated the foot vents. Why? Well because I was moderating the center vents with the center vent wheel thing and overriding the climate control dash control buttons. So as soon as I activated the foot or windshield vent the computer saw I had the temp set for 65 degrees and decided that ment I actually wanted 80 degree air blowing out of the windshield and foot vents until it sensed that the cabin had reached the desired 65 degrees. So in this case the center vent control knob is in conflict with the climate control setting of 65 degrees, which is why I feel that you have 2 devices you must manipulate in order to get the cabin temp to the temp you want it to be. 

So I basically have 2 temperature controls at any given time. I have the buttons on the climate control panel which controls all the vents and I have the center dial control which can be used to manually control only the center vents and I believe it to also have an effect on the side vents next to the windows as well. 

Is there anything I'm missing here? Am I over analyzing the system? I can get the cabin to a temperature I'm comfortable with, so I guess there is no problem with the system as far as I'm concerned but I'm making an observation that in order to get the cabin to the exact temp you find comfortable requires a lot of thought, right?


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## crap_shoot (Dec 29, 2003)

Moderato said:


> Am I over analyzing the system?


Yes!

Just leave it on AUTO with the AC off, auto recirculation on. Then, adjust the center wheel to make your face comfortable, the system will do the rest. If it's raining and the windows fog, turn the AC on. That's it, now you can get to driving the damn thing!


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## salvo (Feb 28, 2004)

You are making it too darn complicated...it maintains the temp you set it at...roughly...but if you want it a bit cooler, then adjust the little wheel...there are so many possible combinations of A/C on or off, auto on, blow at your feet...I begin to think...just roll down the window...(but i live in SD)....my only real complaint, i wish the adjuster in the middle of the vents would light up in red and blue at night...so i could see it. 

does anyone know where the car is taking the temp reading?? (not trying to hijack you thread....)


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## toddkageals (May 5, 2003)

Moderato said:


> First let me say that I love my new E46 and this post is in no way a complaint about the climate control system but rather an opportunity for some of you to comment on my obsevations and a request for help in better understanding how to operate the system. I've also already done a search and read many threads about the climate control in the E46, but I'm still confused about some things.
> 
> First off that center vent wheel thing has me confused. I understand how it works and why some people feel it to be a good feature, but what I'm asking basically is what is the proper way to use it in conjunction with the AUTO climate control system? Should you just put it on the middle white dash setting?
> 
> ...


I keep the center wheel in the middle position, set auto recirc. on, and set the auto temperature setting to 70. I leave the A/C compressor on all the time. I have not touched the climate control since I bought the car (well....not really but practically). The car always manages to get warm/cool quickly and without me even thinking about it. I can GUARANTEE I never thought about it as much as you have  .

Todd


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## bimNaround (Jun 19, 2003)

salvo said:


> You are making it too darn complicated...it maintains the temp you set it at...roughly...but if you want it a bit cooler, then adjust the little wheel...there are so many possible combinations of A/C on or off, auto on, blow at your feet...I begin to think...just roll down the window...(but i live in SD)....my only real complaint, i wish the adjuster in the middle of the vents would light up in red and blue at night...so i could see it.
> 
> does anyone know where the car is taking the temp reading?? (not trying to hijack you thread....)


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## cruztopless (Sep 23, 2002)

toddkageals said:


> I keep the center wheel in the middle position, set auto recirc. on, and set the auto temperature setting to 70. I leave the A/C compressor on all the time. I have not touched the climate control since I bought the car (well....not really but practically). The car always manages to get warm/cool quickly and without me even thinking about it. I can GUARANTEE I never thought about it as much as you have  .
> 
> Todd


This is basically what I do except I have mine at 72. From what I've read the a/c will only activate when necessary so I might as well just leave it on. If it gets a little cool or a little warm I'll adjust the center wheel accordingly.

... and yes, you are over analyzing.


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## s0rce (Nov 16, 2003)

Is there a way for the car to just let in cold air from outside like a vent, because sometimes I just want that but the car doesnt have that function?


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## Moderato (Nov 24, 2003)

s0rce said:


> Is there a way for the car to just let in cold air from outside like a vent, because sometimes I just want that but the car doesnt have that function?


I don't think so, I wish I could set it up so that whatever vents I select have the direct outside air coming in and then I can just dial in the right amount of heat.

One thing I notice is that no matter how I set the system the air coming out of the windshield vents and the foot vents will always be warm. I tried having the air just coming out of the dash vents, set the system to 59 with the AC off (38 outside air temp) but in that case the center vent dial thing didn't seem to effect anything, even at full hot the air was still coming out cold. If I set it to 60 with the same settings and rotated the center knob towards the cold side I was able to get a comfortable air setting. I'm still learning how to use the system, but if I set it for 60 I can get the center vents to a comfortable setting but after a while my feet start to sweat and I can feel the hotter air hitting my face from the windshield vents, so I guess after the car warms up you should de-select the windshield and foot vents, and use the center knob to dial in the exact air temp you want.

I think most of the people who have replied so far are in warmer climates, which I don't think will be a problem, but I like to have the car cool in the winter. Don't you guys wear coats? What do you do take your coat off after the car warms up? Think about it like this: what temp do you have your house set to? maybe 68 - 72. Ok, do you sit in your house at that temp with a winter coat on and shoes, right next to the heater vent? Of course not. I'm just saying that for me it's not as easy as setting the AUTO to 68 and forgetting about it because I get too hot. If I set it for 60 the center vents can be comfortable, but why do the foot and windshield vents stay so hot? There seems to be a big difference between 59 and 60 though, you can hear something happening when you go to 60 from 59, I'm not sure if the 59 setting moderates the outside air temp yet?


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## epc (Dec 24, 2001)

s0rce said:


> Is there a way for the car to just let in cold air from outside like a vent, because sometimes I just want that but the car doesnt have that function?


There are 3 modes for the air circulation mode button: auto, recirculating, and always outside (no light on the button). Select the last mode and you will always get air from outside.


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## epc (Dec 24, 2001)

Moderato said:


> I think most of the people who have replied so far are in warmer climates, which I don't think will be a problem, but I like to have the car cool in the winter. Don't you guys wear coats? What do you do take your coat off after the car warms up?


You think too much. I live in NJ where the temperature goes from 10 to 100 deg F, with snow and rain tossed in. I don't have this problem of getting overheated in my car in the winter, with or without the coat on.


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## mbushnell (Aug 7, 2002)

salvo said:


> ....my only real complaint, i wish the adjuster in the middle of the vents would light up in red and blue at night...so i could see it.


I have the same issue with the climate control - I wish the temp dial for the dashboard vents was lit up.

As far as how I use the system in NJ, I have the temp set at 68 degrees. As for the dashboard vents, last summer I normally kept it at full cold. During the winter, when I start the car cold, I dial it to full hot, and then as the air out of the dash vents heats up, I turn it cooler in small steps, ending up usually somewhere a little cooler than the mid position.


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## s0rce (Nov 16, 2003)

epc said:


> There are 3 modes for the air circulation mode button: auto, recirculating, and always outside (no light on the button). Select the last mode and you will always get air from outside.


but the air is still warmer than the outside air? Sometimes I just want it to be like a window being open but without the rain.


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## Moderato (Nov 24, 2003)

epc said:


> There are 3 modes for the air circulation mode button: auto, recirculating, and always outside (no light on the button). Select the last mode and you will always get air from outside.


Yeah but he was asking is there a way to get outside air into the car that isn't heated? The lowest you can put it on is 59 and that seems pretty cold, in fact it is a lot colder then when it's on 60, and it seemed that the center vent knob doesn't work at all when it's set to 59. So maybe 59 isn't really 59, but rather just that you have the heat completely turned off, it's been hard for me to tell because it hasn't gotten colder then around 37 - 38 degrees here at night. I will do more experimenting with it, until I get this figured out.


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## Moderato (Nov 24, 2003)

mbushnell said:


> I have the same issue with the climate control - I wish the temp dial for the dashboard vents was lit up.
> 
> As far as how I use the system in NJ, I have the temp set at 68 degrees. As for the dashboard vents, last summer I normally kept it at full cold. During the winter, when I start the car cold, I dial it to full hot, and then as the air out of the dash vents heats up, I turn it cooler in small steps, ending up usually somewhere a little cooler than the mid position.


Do you leave the foot and windshield vents on as well? Because if I have it set to 68, like I said before I can get the center vents comfortable with the center knob, but the foot and windshield vents stay hot. 68 is too hot for a coat and shoes on anyway. I bet your house temp is set somewhere around 68, would you be comfortable sitting in your house at 68 degrees with a coat and shoes on, and sitting right next to the heater vents?


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## toddkageals (May 5, 2003)

Moderato said:


> Yeah but he was asking is there a way to get outside air into the car that isn't heated? The lowest you can put it on is 59 and that seems pretty cold, in fact it is a lot colder then when it's on 60, and it seemed that the center vent knob doesn't work at all when it's set to 59. So maybe 59 isn't really 59, but rather just that you have the heat completely turned off, it's been hard for me to tell because it hasn't gotten colder then around 37 - 38 degrees here at night. I will do more experimenting with it, until I get this figured out.


Shouldn't you be able to just put it on fresh air (using the recirc. button), adjust the fan speed manually and turn the temp. to full cold leaving the A/C button off. Wouldn't that give you unheated outside air? The owners manual says that at 59 degrees you are the maximum cooling of the system (since the compressor is off that should mean fresh unheated air)....I guess :dunno:


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## LmtdSlip (May 28, 2003)

Makes me thankful that I have the old manual system.

I have never used an auto HVAC system that I have liked.

Including the original A4, my friends Accord Coupe and a friends E46 and a few GM rental cars. I always end up using the systems manually.


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## RKT BMR (Sep 7, 2002)

This posting is very long -- my apologies. Thorough explanations just don't lend themselves to "sound bites". Hopefully what I share here can help Moderato and others better understand some of the nuances with climate control systems, and how to interact with them


Moderato said:


> Yeah but he was asking is there a way to get outside air into the car that isn't heated?


Turn the center vent wheel all the way to three blue dots, turn off the AC, and set the temperature on the climate control to the coldest setting (59F, I believe). This will give you the coldest "vent" air possible.

However, it will still be a few degrees warmer than the temp outside. The reason for this is that it passes through the engine compartment, which is quite warm. The grill on hood right in front of the windshield -- where the windshield washer jets are -- is the intake for cabin ventilation. open your hood and you can see the air filter housing right undernealth this grill. That housing sits right above the motor, and gets quite warm when the motor is at operating temperature.

As the outside air passes through the filter housing, it picks up a little bit of heat through conduction, warming a few degrees. Can be as much as 4-6 degrees of warming. You can minimize this effect by setting your vent flaps to the floor vents and dash vents (minimizes airflow resistance), and cranking the fan up to its maximum setting. This moves the air through as fast as possible, minimizing the time it's in contact with the warmer air filter housing.

Now, all that said, you're really better off just leaving the AC on all the time, regardless of the temperature outside, with a set temperature for the climate control system that you don't monkey with very often, and leaving the vent and fan controls on auto. Then, just use the center vent wheel to make fine adjustments for comfort while you drive. Use the center wheel adjustment _liberally_, but in relatively small increments until you get a confortable situation for the particular conditions you are driving under at that time.

On any extended trip of more than 30 minutes or so, you will probably have varying conditions, and will probably have to tweak the center wheel from time to time on the trip to maintain your comfort level. This is not a sign of a poorly operating or badly designed system, but rather a reflection of the fact that the system doesn't monitor your subjective comfort, but rather the objective temperature of the interior cabin air. One's perception of comfort is very dynamic, affected by things like incident solar radiation through the windows on the upper body, vs. overcast conditions; the stress level of the person in question; effects of medications; well-slept or deprived; and many more.

So, at one time, sitting in a car where the air is measurably 68° you feel really comfortable. 20 minutes later, right after an 18-wheeler almost ran you off the road, your forehead is beading sweat and you feel hot and sweaty in your shirt, but the cabin air temperature is... 68°. You feel uncomfortably hot, and crank down the temp, crank up the fan, aim the vents at you, and go, "ahhhhhhhhhhhhh!"

These sorts of perceptive variations are what make the BMW center-vent-tweak-knob such a brilliant feature in truth, but BMW does a pis-poor job of explaining why it's so useful.

Finally, about that AC again: As I said, leave it on all the time. Do not be concerned about wasting fuel. The BMW compressor uses a variable thrust-plate design, which in simpler terms means that it can vary it's compression output based on demand. The sophisticated climate and engine management system take maximal advantage of this, making for an extemely efficient cooling model. This is why you don't hear/feel the compressor cycling on and off like you do in some other cars -- it doesn't. It varies continuously based on the cooling demands of the situation.

Therefore, when it's cold and overcast outside, the compressor places a very minimal load on the motor, negligible enough that you wouldn't notice a meaningful difference in gas mileage if it were off completely. However, it does function enough to keep the cabin air dry, avoiding window fogging and aiding comfort.

The only time I turn off my climate system completely is when I put the top down. Makes no sense to have it on when there isn't a closed cabin.


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## brkf (May 26, 2003)

RKT BMR said:


> Now, all that said, you're really better off just leaving the AC on all the time, regardless of the temperature outside, with a set temperature for the climate control system that you don't monkey with very often, and leaving the vent and fan controls on auto. Then, just use the center vent wheel to make fine adjustments for comfort while you drive. Use the center wheel adjustment _liberally_, but in relatively small increments until you get a confortable situation for the particular conditions you are driving under at that time.


Then it's not auto climate control. Personally, I hate the system as its temperature readout has nothing to do with the system trying to warm or more often cool the cabin down.



> On any extended trip of more than 30 minutes or so, you will probably have varying conditions, and will probably have to tweak the center wheel from time to time on the trip to maintain your comfort level. This is not a sign of a poorly operating or badly designed system, but rather a reflection of the fact that the system doesn't monitor your subjective comfort, but rather the objective temperature of the interior cabin air.


Again, a good auto climate control system attempts to match the set temp to the car's temp quickly. If I get into my car and it's 85 miserably hot degrees outside and I have the climate control set to 65, then the system should blast freezing air until 65 degrees is met.

In fact, the ridiculous system will blast hot air (anything over 68 degrees) if the setting is in the middle for hours, never cooling the car. I must adjust the stupid dial to 3 blue dots to get the car to cool down. That's not auto climate control. That's Karl Climate Control.



> So, at one time, sitting in a car where the air is measurably 68° you feel really comfortable. 20 minutes later, right after an 18-wheeler almost ran you off the road, your forehead is beading sweat and you feel hot and sweaty in your shirt, but the cabin air temperature is... 68°. You feel uncomfortably hot, and crank down the temp, crank up the fan, aim the vents at you, and go, "ahhhhhhhhhhhhh!"


Ah no. Make it 68 degrees and keep it that way without me ever touching a dial. If I want it warmer, god forbid, I should be able to click the temp up a few notches. At that point the system should jump into action to give me a warmer temp instantly. Colder? Same deal. This won't happen using BMW's dimwit design.



> These sorts of perceptive variations are what make the BMW center-vent-tweak-knob such a brilliant feature in truth, but BMW does a pis-poor job of explaining why it's so useful.


Manual control of a so-called auto climate control system is brilliant?



> The only time I turn off my climate system completely is when I put the top down. Makes no sense to have it on when there isn't a closed cabin.


I grew up with convertibles and have always run the AC with the top down. What? Yep, when I'm sitting at a light it's nice to have cool air still hitting you. When on the open road and it's hot - ie over 70 degrees - it's nice to have cool air in the cabin, even if warm air is swishing around.

I can't recall ever driving in a convertible without the AC going...oh wait, I think my sister refused to use AC in her Miata. "We live in San Diego..." Uh, yeah, it's still damn hot.


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## Moderato (Nov 24, 2003)

Thanks for all these detailed replies everyone. I will experiment with leaving the AC on all the time, but I must admit that I have a real brain block concerning that. It's just hard for me to switch on the AC when the outside air is 40 degrees, however this variable compressor design is something I've never had in any of my previous cars so I will try this idea with an open mind.

It's true that BMW is very vague regarding the center wheel thing in the owner's manual.

I've noticed that if I set the car for 60 on full AUTO (A/C off) that the air coming out of the center vents can be comfortable if you turn the dial to 3 blue dots. However the air coming out of the foot vents will roast my feet, so I have to shut them off. The air coming out of the windshield vents will also remain hot and I sit rather upright so I can feel the hot air from those vents hitting my face so I have to shut those off. This will work for a while but the windows will start to fog, so I guess leaving the AC on will eliminate that problem, I have to try that.

59 is a mysterious setting. Tonight it was 40 degrees out and I was able to find a comfortable setting at 59, with the center vent on 3 red dots and the foot and windshield vents on. Wierd thing is this, If i rotate the center knob back to the center, and put the system back in AUTO on 60, just one degree higher...all of a sudden the air gets really hot and there is a disinctly different smell that comes out of the vents, after a couple of seconds that smell seems to go away. But the foot and windshield air will stay hot and I've have to disengage them and go back to just the center vents with the center knob back to the 3 blue dots. 

I will keep experimenting with this system and force myself to leave the AC on the whole time tomorrow night and see what happens.


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## salvo (Feb 28, 2004)

nice!


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## mbushnell (Aug 7, 2002)

RKT BMR said:


> Just a nitpicky clarification... Those aren't wires, but rather a conductive material that is painted on.


Well, they look like wires...


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## bimNaround (Jun 19, 2003)

salvo said:


> I know, but that requires atleast three or four presses....sorry i should have been more clear...that would be funny if I never could turn the thing off...Im sure there are those people out there! :rofl:


It could be just two presses. Hold down for a couple of seconds, release, press once more and then OFF.


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