[A2Z]

Greetings,

It's summertime now so I leave the temp at 60 F and leave the circulation in auto so it can filter pollutants and stuff. But sometimes the climate control system blows cold air (almost like it knows I'm feeling hot) even though the a/c button is not on. I had a meeting with the "BMW Geniuses" a couple of weeks ago at my dealer and asked them about this and they tried to explain it by saying maybe there was some leftover cold air in the system or that the metal piping in the cooling system was cold. Well BMW would need to have put a fridge in the car to keep the air cold or something because I would leave the car off overnight before turning it on in the morning and experiencing this. Just want to know if I'm the only one and if there was some explanation for this?

Thanks!

[xG35c]

The best guess I've read is the humidity sensor activates the compressor as needed, even if you have the windows open. Only way to keep it off is to shut off the climate control (which I don't mind too much if I have the windows open).

[kriszty]

i have the same problem, although the airco switch is off, sometimes it,s going automatic on , if i switch it on and off again, it switches off.

is there no coding possible to switch off this sensor ?? , if i want to switch on the airco, i want to do that by myself , and not any kind of sensor !!

[DDD31]

I've noticed on my car that if you shut off the car with the a/c on, the next time you start the car the a/c will run for a couple of minutes blowing cold air even if the a/c is immediately switched off after starting.

If I shut off the car with the a/c switched off, the next time I start the car the a/c is off and does not blow cold air at all until I turn the a/c on.

Strange.... But I'm sure zee Germans have some logic behind it.

[....,,,,..,,..]

It's all part of the modern HVAC system.

Invariably it's doing its job.

I believe it's probably picking up in car climate / humidity and automatically cooling / adjusting humidity levels.

Personally, you just leave it on auto with air conditioning on, then control temperature by keeping it on say 16.5 c or 21.5 c etc and fine control with the thumb wheel.

[Buckeyes]

Nice story from the BMW Geniuses. Haha. From playing around with the setting it seem that if in auto mode the car will do what it needs to do to keep temp at whatever it's set at regardless of the AC light. To completely turn off the AC you need to turn off auto and AC.

[A2Z]

Originally Posted by Trcb777

Nice story from the BMW Geniuses. Haha. From playing around with the setting it seem that if in auto mode the car will do what it needs to do to keep temp at whatever it's set at regardless of the AC light. To completely turn off the AC you need to turn off auto and AC.

Yeah, I found their explanations amusing . They told me that no one had brought this "issue" to them before. In any case, the auto and a/c buttons are not on when this happens. The only thing that I would occasionally leave on is the circulation button in automatic mode. And even then, with the circulation button off I have had cold air blowing.

This is not a showstopper or a major issue. I have never experienced this in any previous car I have owned and just wanted to know more about how the HVAC works in this car since the "Geniuses" really could not explain this. So I figured I would turn to the "Geniuses" on the forum .

[Billfitz]

If you put the temp at 60 in auto mode and the outside air is too warm to take the car down to 60 then the AC will engage to take the car down to the temperature you've set it at. By the same token if the outside air temperature is 30 the car will engage the heater to give you the 60 degrees you asked for.

[A2Z]

Originally Posted by Billfitz

If you put the temp at 60 in auto mode and the outside air is too warm to take the car down to 60 then the AC will engage to take the car down to the temperature you've set it at. By the same token if the outside air temperature is 30 the car will engage the heater to give you the 60 degrees you asked for.

I understand that, but my car isn't even in auto mode and it still turns on the a/c when it feels like it. I can understand if the car was in auto and it maintained the temp at 60 F, but it's not and still adjusts the temp. Never had this happen in previous cars so I am just trying to make sense of this. Thanks!

[fshubert]

BMW needs to control the A/C by the A/C switch on the dash. LED lit, A/C on. LED off, A/C off. This switch should override anything else the HVAC system wants to do.

[murrays]

My AC stays off most of the time when I start the car (car in the sun, outside temp in the 80s, inside temp set to 70). The AC has behaved a bit odd and I think it has to do when I've turned the AC on with the AC switch vs. turning Auto off/on.

Put another way, if I want the AC on, I press the Auto button which turns it off, then turn it on. I then hit the AC button if I want it off.

So yes, I've been confused by this as well.

[larrylam646]

I too noticed the HVAC system continued to produce cooling for some time after turning off the AC. I suspect it has something to do with the start-stop system.

My best guess is the HVAC contains a thermal storage unit that continues to provide cooling/heating when the start-stop system is enabled eg. the engine is shut off at a stoplight.

Larry

[murrays]

Originally Posted by larrylam646

I too noticed the HVAC system continued to produce cooling for some time after turning off the AC. I suspect it has something to do with the start-stop system.

My best guess is the HVAC contains a thermal storage unit that continues to provide cooling/heating when the start-stop system is enabled eg. the engine is shut off at a stoplight.

Larry

It's a bit more than that since it seems to continue after the car has been turned off for some time. There's a couple things like that where I'd like to understand the logic so I know what I'm doing.

[Fronzdan]

This is "normal" behavior. As xG35c mentioned above, it is the humidity/window fog sensor that does this. If it thinks the conditions are right for the windows to fog up, it will turn on the compressor, regardless of what you have Auto and Ac buttons set at.

I don't like it either. Mine kicked in today as a matter of fact, on a rainy Summer day. Temps are low ~65-70 degrees, high humidity. You basically freeze your ass off, but the windows are clear. I've always managed to keep the windows clear in other cars by pulling in fresh air, raising the temp a bit and directing onto the windshield...no compressor needed. But the BMW HVAC wants to do it this way. There is no way to override it.

[HighlandPete]

Originally Posted by Fronzdan

This is "normal" behavior. As xG35c mentioned above, it is the humidity/window fog sensor that does this. If it thinks the conditions are right for the windows to fog up, it will turn on the compressor, regardless of what you have Auto and Ac buttons set at.

.... There is no way to override it.

I can't find the exact working strategy for the F3x HVAC systems, but from BMW data it does appear to intervene automatically.

The new BMW 3 Series is also equipped with an automatic sensor-controlled anti-fogging function, which intervenes by means of targeted ventilation as soon as visibility is restricted.

I know we can read that to apply with or without the AUTO function, but it does appear different than the system in the E9x models, where the condensation anti-fogging sensor only worked in Auto mode.

The problem in the E9x IHKA systems, if the A/C function was off, there was a complex strategy to clear the screens, which could involve lots of airflow and heating the air to prevent misting. I'm very aware of that function (have the staged strategy listed in a BMW document), as I got involved with BMW and the IHKA designers, after BMW logged data from my car in real time, to try and find why the climate control appeared to go wrong when on AUTO and the A/C was off.

I can see the logic of using the A/C to do the demisting job, in preference to the older strategy, makes total sense to do so.

Where I think some of you guys get a cold blast, you don't run a mid range temperature, or you'd not really notice the A/C function kicking in and out.

I run 20C in my 5-series, unless the system is trying to cool the cabin, there is no cold air blast. The HVAC system is not intrusive at all, even when dehumidifying, air temperatures don't change.

HighlandPete

[Chris@codemybimmer]

Mine does the same thing.

I think when its too humid/hot the AC will turn on to cool the head unit.

when i was doing the NBT retrofit i noticed that cold air comes out from the back of the head unit area. maybe it cold be the cars way of cooling down the electrical equipment when it needs to

If anyone had taken out the head unit you'll notice how hot that thing is if it has been running for some time.

[murrays]

Originally Posted by Fronzdan

This is "normal" behavior. As xG35c mentioned above, it is the humidity/window fog sensor that does this. If it thinks the conditions are right for the windows to fog up, it will turn on the compressor, regardless of what you have Auto and Ac buttons set at.

I don't like it either. Mine kicked in today as a matter of fact, on a rainy Summer day. Temps are low ~65-70 degrees, high humidity. You basically freeze your ass off, but the windows are clear. I've always managed to keep the windows clear in other cars by pulling in fresh air, raising the temp a bit and directing onto the windshield...no compressor needed. But the BMW HVAC wants to do it this way. There is no way to override it.

There's a bit more to the story than the window sensor IMHO, but haven't quite put my finger on it.

[m_alnimah]

With the 117 Degrees we get here that's HEAVEN... Care for a 2015 F15 M Sport in exchange for your car?

[RM7]

Originally Posted by Fronzdan

This is "normal" behavior. As xG35c mentioned above, it is the humidity/window fog sensor that does this. If it thinks the conditions are right for the windows to fog up, it will turn on the compressor, regardless of what you have Auto and Ac buttons set at.

I don't like it either. Mine kicked in today as a matter of fact, on a rainy Summer day. Temps are low ~65-70 degrees, high humidity. You basically freeze your ass off, but the windows are clear. I've always managed to keep the windows clear in other cars by pulling in fresh air, raising the temp a bit and directing onto the windshield...no compressor needed. But the BMW HVAC wants to do it this way. There is no way to override it.

This would make sense. I live by the ocean (kind of) and the air temperature here is never super warm, although objects heated by the sun for 20 hours during the day can get that way. I've noticed cold air coming out of the vents almost all the time, regardless of the selections like you say. I even turned the temp up significantly to see what it would do, in the intermediate temps it felt like I was getting hot and cold air coming out, not that it was overwhelming, it just felt distinctly like the A/C was still on, like when you're running the defroster. This explanation would make more sense. I'm not sure I want the defroster on if I put down the windows...wish there was a way to disable this.

[S4NoMore]

Originally Posted by Fronzdan

You basically freeze your ass off, but the windows are clear.

If you're freezing your ass off, use the Comfort knob at the dash vents to dial in a tad less cold / more heat. I've found this to be highly effective, so I'd recommend only very minor adjustments until you're happy.

[S4NoMore]

Originally Posted by murrays

It's a bit more than that since it seems to continue after the car has been turned off for some time. There's a couple things like that where I'd like to understand the logic so I know what I'm doing.

I'm a little obsessive about my car and it's settings so I don't like the Auto climate control to come on every time I start the car. I'm sure it's smart enough to unload the system on its own, but this is a habit of mine. I coded both the fan and the AC to remember last setting, and I'll usually turn off the AC when I get home or sometimes even the entire Auto system.

I park in a garage, and in the morning I might turn the Auto back on (+ button) (or leave it running if I didn't turn it off previously) without the AC. I've found that the noise of AC is still there for awhile, and the air feels conditioned longer than I might have expected before "running out of cold." This occurs even after the car sat for around 12 hours or so.

My understanding, an educated guess I suppose, is that the refrigerant ("freon" is a misnomer for the stuff that is compressed by the compressor and then cools air behind the dash at the evaporator - the cold counterpart to the heater core) still has working properties for a fair amount of time even with the AC shut off. It remains compressed perhaps because this modern system is so good.

My car is a manual and the AC behavior might be more noticeable compared with automatic cars, and I can confidently say that I have not experienced the AC compressor working on its own, without the button pressed and the LED lit. Foggy, humid, whatever... I reach a point several minutes into my morning drive when the outside cool air is not cutting it and I turn on the AC.

[Heel328]

I hate it.

I have a 2013 328i MT and my AC seems to run without the AC light ON. Drives me nuts. On a nice day when AC is not needed I just turn the whole damn system OFF.

As soon as summer is over I might pull the AC fuse for the winter.

Too much computer on this car.