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Discussion Starter · #1 ·
I'm not clear from reading the manual about the AC and the climate control. Does the AC kick in automatically to lower the temperature, or do I have to set it manually. I have the automatic climate control, so I assume the AC would be initiated to maintain the desired temperature.
 

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docbenjy said:
I'm not clear from reading the manual about the AC and the climate control. Does the AC kick in automatically to lower the temperature, or do I have to set it manually. I have the automatic climate control, so I assume the AC would be initiated to maintain the desired temperature.
No, you have to turn on the AC manually. So, the system isn't 100% automatic as one would think.

I think the reason for this is so that we can turn it off, 100% off. Having a separate switch for AC allows you to still use the auto mode with it off, situations like when you're climbing a steep hill and you want to switch it off to avoid overheating the engine. And in performance driving when you don't want the draw of the compressor on the engine.

I may know what you're gonna say next... But Lexus and Acura's have 100% automatic climate controls that engage the AC when needed. I agree, I expected it to work this way as well, but I also understand why it doesn't.
 

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jvr530i said:
No, you have to turn on the AC manually. So, the system isn't 100% automatic as one would think.

I think the reason for this is so that we can turn it off, 100% off. Having a separate switch for AC allows you to still use the auto mode with it off, situations like when you're climbing a steep hill and you want to switch it off to avoid overheating the engine. And in performance driving when you don't want the draw of the compressor on the engine.

I may know what you're gonna say next... But Lexus and Acura's have 100% automatic climate controls that engage the AC when needed. I agree, I expected it to work this way as well, but I also understand why it doesn't.
Hmm, I'm not sure how you reached that conclusion...at least for the 3 series.

Actually, when you press the "AUTO" button, the AC compressor is automatically on, as indicated by the green light on the "snowflake" button. So, the answer is "yes", the AC compressor is used as needed in auto mode. The separate button is more for the purpose of overriding the auto function to disable the compressor. In freezing temperatures, I believe although the AC light is still on, the compressor is not used.

In more moderate temps, you can press the AC switch to turn it off (i.e., "vent" function)and retain all other auto functions such as air distribution and volume. You can go to full manual by pressing any of the 3 distribution buttons (floor, dash, windshield) and control fan speed separately. This gives the best of all worlds. So, my conclusion is that the BMW climate control is 100% auto unless you take steps to override it.

The Acura system works in a similar way on our '03 TL. The difference is, all of the functions are not displayed when in full auto mode. If you override the AC mode, then the "on" or "off" status will be displayed ("on" is the default). If you change air direction then you will see the mode information on the screen. The fan speed is not displayed in the LCD window because a knob is used for manual air volume and you can visually see where the knob is positioned.
 

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The funny thing about the climate control is the way it detects temperature. If it's kind of cool out - ie low 70s, and I have the climate control set to 66 or so, the air it pumps out is just slightly cool (even with the blue/red dial set to all blue). Sometimes I find I have to lower it to 60 just to get the air stream cooler. However if its 85 outside, then 70 pumps out ice cold air. Weird.
 

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Did someone ever experience the following scenario: cold air from dash while WARM air from floor when ac is set to automatic?? This happened to me this other night. I cant recall the exact settings and outside temp at the time. But I have a feeling that the outside temp. at the time was just slightly higher than the target temp I set on the ac. Anyway I was like WTF and have been using the ac manually ever since.

And yes the AC is okay, but not defintely not "cold". My friend has a 98 toyota tacoma. I'd call that cold, no actually its freezing. Sigh, way to go for German eletronics.
 

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No, markl53 and walc are incorrect. You have to push the snowflake button to turn the compressor on or off. There is a key memory setting that will turn the compressor on automatically upon starting the car if you so desire. (This could be the source of their confusion.) I have one key set to do that...my "summer key" and the other key is set not to do that...my "winter" key.
 

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startover said:
Did someone ever experience the following scenario: cold air from dash while WARM air from floor when ac is set to automatic?? This happened to me this other night. I cant recall the exact settings and outside temp at the time. But I have a feeling that the outside temp. at the time was just slightly higher than the target temp I set on the ac. Anyway I was like WTF and have been using the ac manually ever since.
Yeah, mine seems to do this as well. I took delivery in mid-December (cold weather) and right away I noticed that apparently as the target cabin temp is nearly reached with heat, the dash vents come on with cold air. I deal with this by dialing in the 2 red dots to slightly warm that dash air. This happens all the time. In most other cars I've owned with automatic climate control, they usually utilize the upper windshield vents in heat mode to give some indirect cooler air through the cabin rather than the main dash vents.
 

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It may be different for other model years, but according to the manual for my '05 330:

- When Auto is on, the compressor is always running - when it's cold out, the conditioned air is reheated to meet the correct temperature. I know that when I hit Auto, the Snowflake button also lights up.

- You can change the temperature of the air coming out of the dash vents using the red/blue button knob on the center vent - so the temperature can be different out of the floor vent and the dash vent
 

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MysticBlue said:
No, markl53 and walc are incorrect. You have to push the snowflake button to turn the compressor on or off. There is a key memory setting that will turn the compressor on automatically upon starting the car if you so desire. (This could be the source of their confusion.) I have one key set to do that...my "summer key" and the other key is set not to do that...my "winter" key.
I'm not talking about automatically turning on the compressor when starting up. Try this test and report back please...

Start car and with the climate control on (in any mode), turn off A/C (snowflake green light off). Press "auto" switch and see what happens. Does the snowflake light turn back on? Use both keys and my bet is you get the same result -- yes, the snowflake (A/C) will turn on with a press of the "auto" button.

I thought that the key memory feature "re" turns on the A/C if it had been left off from the prior use of the vehicle. I thought that that is totally independent of how the "auto" button functions. If I am incorrect, then that means that the key memory feature actually disconnects the A/C snowflake button completely from the "auto" function.
 

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FWIW, I definitely think that the climate control in my '04 325i does not work as well as the system in my previous car, a '98 A4. On the A4, about all I ever did was to set the temperature either at about 68 in the winter or about 74 in the summer, and it was always comfortable under most conditions.

OTOH, in my E46 I have to fiddle with things a lot more. In cool weather, I have to set the temp at about 62 or it gets too hot. The dash vent knob also needs a lot of adjustment, as it sometimes blows warm air in my face. It is nice, though, on those cool but sunny days when you need cabin heat on your feet, but want cool air on your face.

Another thing I noticed on really cold days is that it seemed to kick the blower up to a really high speed before things had really warmed up enough to make heat, and I would have to manually turn it down for a few minutes. I have no idea what it thought it was doing :dunno: .

Now that I'm used to it I can certainly live with it, but my Audi was definitely better in this area (plus a better sound system, but that's another story...).
 

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icemanjs4 said:
The funny thing about the climate control is the way it detects temperature. If it's kind of cool out - ie low 70s, and I have the climate control set to 66 or so, the air it pumps out is just slightly cool (even with the blue/red dial set to all blue). Sometimes I find I have to lower it to 60 just to get the air stream cooler. However if its 85 outside, then 70 pumps out ice cold air. Weird.
This is due to how the IHKA determines "Y factor", a cooling parameter that is the output of an algorithm that has as its inputs outside temp, interior temp, heater core temp, user demand (where you have the desired temp set), A/C coolant pressure, incident solar radiation, and a few other things. Basically, the Y factor is then used to control the servos that operate the vent and mixing flaps, and the blower speed.

The IHKA controller accounts for the fact that when it is very hot outside relative to the interior temperature the rate of heat intrusion (and therefore loss of cooling) is greater. IOW, more heat has to be removed from the cabin per unit time than if the air outside is closer to the inside temp. So, it adjusts for this first by blowing colder air in to the cabin, which is less annoying to most people than a blasting fan, and then when the limit is reached (i.e. compressor running full load, recirc flap closed, all circulation going through A/C exchanger) it starts to crank up the blower and move a larger volume of air through the cooling system.
 

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markl53 said:
I'm not talking about automatically turning on the compressor when starting up. Try this test and report back please...

Start car and with the climate control on (in any mode), turn off A/C (snowflake green light off). Press "auto" switch and see what happens. Does the snowflake light turn back on? Use both keys and my bet is you get the same result -- yes, the snowflake (A/C) will turn on with a press of the "auto" button.

I thought that the key memory feature "re" turns on the A/C if it had been left off from the prior use of the vehicle. I thought that that is totally independent of how the "auto" button functions. If I am incorrect, then that means that the key memory feature actually disconnects the A/C snowflake button completely from the "auto" function.
Maybe things have changed after MY03, but on mine, this is how it has always worked, and yes, I checked it again.
If you DO NOT have the key memory selected to start the compressor, there is only ONE way to turn it on and only ONE way to turn it off and that is to push the button. The "auto" button has absolutely no effect on it, on or off.

If you DO have the key memory selected to start the compressor, there are two ways to start the compressor. The first is to start the car. If you then push the button, it turns off, which brings up the second way to turn it on, which is to push the button again. At no point in any of these scenarios does pushing the auto button have any effect.
 

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Dave that's a great explanation. It kind of goes along with what I figured. Why stress the compressor if it has very little room to go. The downside is, while the cabin is the correct temperature, you lack that nice cool air feeling on your face and hands. Even when the temp is right, i sometimes enjoy that extra cool rush, so I find myself turning down the AC to 61 degrees temporarily. On the flip side, on those hot days, it does a great job of cooling off the car fast, but then, the car actually gets too cold - heheheh Boy am I picky :rofl: By the way, where do you find out the technical information and algorithms for various parts of the car - if there's a repository, it might make for some interesting bedtime reading.

RKT BMR said:
This is due to how the IHKA determines "Y factor", a cooling parameter that is the output of an algorithm that has as its inputs outside temp, interior temp, heater core temp, user demand (where you have the desired temp set), A/C coolant pressure, incident solar radiation, and a few other things. Basically, the Y factor is then used to control the servos that operate the vent and mixing flaps, and the blower speed.

The IHKA controller accounts for the fact that when it is very hot outside relative to the interior temperature the rate of heat intrusion (and therefore loss of cooling) is greater. IOW, more heat has to be removed from the cabin per unit time than if the air outside is closer to the inside temp. So, it adjusts for this first by blowing colder air in to the cabin, which is less annoying to most people than a blasting fan, and then when the limit is reached (i.e. compressor running full load, recirc flap closed, all circulation going through A/C exchanger) it starts to crank up the blower and move a larger volume of air through the cooling system.
 

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Discussion Starter · #17 ·
Here's a follow up..
Weather is warming up, and I noticed something with the AC. I turned off the fan, then pressed auto, and lo and behold the AC turned on. I manually turned off the AC. The auto button remained lit, and the display still showed "auto". I then pressed the auto button, and the AC came back on!!
Furthermore, if I turn the car off with the AC on, as we know the AC turns on when I start the car again. If I turn off the car with the AC manually turned off, when I start the car the AC is off. If I then press the "auto" button, the AC comes back on. Is it possibele that there are 2 auto settings, such that pressing it a second time reactivates the AC circuit?
 

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docbenjy said:
Here's a follow up..
Weather is warming up, and I noticed something with the AC. I turned off the fan, then pressed auto, and lo and behold the AC turned on. I manually turned off the AC. The auto button remained lit, and the display still showed "auto". I then pressed the auto button, and the AC came back on!!
Furthermore, if I turn the car off with the AC on, as we know the AC turns on when I start the car again. If I turn off the car with the AC manually turned off, when I start the car the AC is off. If I then press the "auto" button, the AC comes back on. Is it possibele that there are 2 auto settings, such that pressing it a second time reactivates the AC circuit?
I think it might work a little simpler than you might be making it. When you press the "AUTO" button, it puts everything back to the default modes for the full automatic function. This includes fan speed, air distribution direction and A/C compressor ON. If you manually make adjustments, pressing the "Auto" button will always return all the pieces back the the defaults, see? So it makes total sense that if you manually press the A/C button to turn off the compressor, pressing "Auto" will turn it back on. Now, if you do turn off the A/C, the "Auto" will still show up on the display screen because than fan is still in auto mode unless you also manually press the fan up or down buttons. That "AUTO" designation is really indicating auto fan. The only time the green LED on the "AUTO" button goes out is if you choose an air distribution direction manually. In any event, the pressing of "Auto", as I said, returns all functions back to normal -- auto fan speed, auto air distribution direction, A/C compressor on. So really, there are 2 auto indicators, the green LED on the "Auto" button signifying auto air distribution and "AUTO" on the display which indicates auto fan function. The green LED on the A/C of course shows its mode as on or off.
 

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Discussion Starter · #19 ·
markl53 said:
I think it might work a little simpler than you might be making it. When you press the "AUTO" button, it puts everything back to the default modes for the full automatic function. This includes fan speed, air distribution direction and A/C compressor ON. If you manually make adjustments, pressing the "Auto" button will always return all the pieces back the the defaults, see? So it makes total sense that if you manually press the A/C button to turn off the compressor, pressing "Auto" will turn it back on. Now, if you do turn off the A/C, the "Auto" will still show up on the display screen because than fan is still in auto mode unless you also manually press the fan up or down buttons. That "AUTO" designation is really indicating auto fan. The only time the green LED on the "AUTO" button goes out is if you choose an air distribution direction manually. In any event, the pressing of "Auto", as I said, returns all functions back to normal -- auto fan speed, auto air distribution direction, A/C compressor on. So really, there are 2 auto indicators, the green LED on the "Auto" button signifying auto air distribution and "AUTO" on the display which indicates auto fan function. The green LED on the A/C of course shows its mode as on or off.
If I understand what you are saying, the AC compressor will come on automatically to lower the temperature. That seems to conflict with some of the threads which implied that the AC had to be initiated manually, as opposed to other systems such as the Acura. This would be more logical in a truly automatic climate control system. BTW, the green LED beside the auto button stays lit even when the AC is turned off.
 

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docbenjy said:
If I understand what you are saying, the AC compressor will come on automatically to lower the temperature. That seems to conflict with some of the threads which implied that the AC had to be initiated manually, as opposed to other systems such as the Acura. This would be more logical in a truly automatic climate control system. BTW, the green LED beside the auto button stays lit even when the AC is turned off.
I think it was determined in one of the responses that someone's (MysticBlue) '03 3-series didn't behave the way my '05 does -- that is, the A/C is engaged whenever you press the "Auto" button. Some people also think that when the A/C is engaged, this means cold air is always coming out of the vents -- that isn't correct. Depending on the temperature needed, hot air can still come out even with the compressor engaged -- this is how dehumidifed, heated air is used to clear the windshield in defrost mode. The 2005 BMW 3-series has as much an automatic system as you can have, IMO. You can manually override any function if you want to yet pushing "Auto" will do it all. (OK, the only confusing matter is the manual temp wheel on the center vent -- that's up to you to a certain extent.)

PS - always engage the A/C compressor when it is damp outside, even if it's not very hot -- ever see people who can't get their windows clear? They don't have their A/C engaged even in moderate to cool temps. Sometimes you need to override the system and select upper and windshield vents and kick up the fan speed to get enough dehumidifed air circulating to clear the windows.
 
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