[AWheeler]

Whether I have the A/C button depressed or not, the A/C seems to turn on by default when I start my car and ~50% of the time when I turn the climate control on while driving.

e.g. car is started --> climate control is automatically turned on and A/C compressor click heard --> however, A/C button is not depressed and A/C light is not illuminated.

I understand BMW has programmed the car such that the climate control turns on every time I start the car after after what seems like >15-20 minutes of rest. However, the A/C seems to turn itself on without me pressing the A/C button. Have others experienced this?

Yes, I know it is a relative nit-pick. Perhaps I need to RTFM?

[3.0L]

Originally Posted by AWheeler

Whether I have the A/C button depressed or not, the A/C seems to turn on by default when I start my car and ~50% of the time when I turn the climate control on while driving.

e.g. car is started --> climate control is automatically turned on and A/C compressor click heard --> however, A/C button is not depressed and A/C light is not illuminated.

I understand BMW has programmed the car such that the climate control turns on every time I start the car after after what seems like >15-20 minutes of rest. However, the A/C seems to turn itself on without me pressing the A/C button. Have others experienced this?

Yes, I know it is a relative nit-pick. Perhaps I need to RTFM?

What temperature do you have your climate control/s set to? 68? 72? Something higher or lower?

This could be a factor.

[AWheeler]

Interesting, it has been set at 62 lately now that it is warm out. I will try putting it up around 70 when I shut down with A/C off.

[huma]

Was going to make a similar post. My a/c randomly turns on as well. Auto and AC buttons are both off. The only button that's on is the A for air circulation and temp is set at 75.

[overcoil]

As someone eluded to sometime back - it MAY be a feature to keep seals lubrucated or the system primed.

[Declio]

Kinda noticed this today. Was driving home and it's the first cool-ish day since I've gotten the car (about 70 F). I turned the AC button off and had the auto set to like 72 and it was blowing COLD air...like no way it was just air coming from the outside. Seems to activate AC whether or not that button/light is on when in auto mode.

[sstarrx3]

I think my last three cars have behaved like this...AC is on by default. Regardless of the temps. I think its to optimize the humidity in the car. Even in the winter it helps clear your windows faster.

[OpenAir]

Do you drive in ECO mode? It has an additional setting for climate control.

[pikcachu]

I think the car will turn on the AC to if the condensation sensor signals it...regardless if the AC button is on or not

[jtzako]

Mine is set to 70 and so far I haven't seen the AC turn on. Its set to Auto, middle fan speed, and those stay set of course. I am in Colorado though, so theres about no chance of a moisture sensor triggering...

[moldcad]

Guys, with a car like the M235i the surplus of power is so huge that I really wouldn't treat all this as a problem. My A/C is always on - and not because it has a mind of its own, but because I WANT it that way. It allows for always the same air quality (not just temperature) inside the cabin - and I've used A/C that way with all my BMWs (i.e. on 365 days a year)...

[pikcachu]

Originally Posted by jtzako

Mine is set to 70 and so far I haven't seen the AC turn on. Its set to Auto, middle fan speed, and those stay set of course. I am in Colorado though, so theres about no chance of a moisture sensor triggering...

It's not the moisture outside the car but the humidity in the cabin that generates from breathing for example that fogs the windows....

[bimmerfile]

I've noticed this anomaly several times and have also wondered if it was some bug in the software controlling the A/C.
It's not usually a problem except on cool mornings when the cabin is already cooler than I would like only for the A/C to come on with a blast of extra cold air.

[jtzako]

Originally Posted by pikcachu

It's not the moisture outside the car but the humidity in the cabin that generates from breathing for example that fogs the windows....

Yeah, that would require a significant amount of time sitting with the car off.. Its very dry here in CO, fogging windows is pretty uncommon.

[Merc for hire]

The car seems to have a smart moisture sensor inside. Whenever the window starts to fog, the AC would come on without any lights to clear the fog. Even when car is sitting still with engine auto-off. It would kick the engine on.

[AWheeler]

Thanks to all for the interesting discussion. I would suspect the A/C is turning on in response to high cabin moisture, as others suggested. I will ask my service advisor next time I visit the dealer out of curiosity.

[RPM90]

Page 136 in the owners manual has info on the HVAC system.
In short, when using the HVAC system in "auto" mode the system will use temp and humidity/condensation sensors to determine if AC compressor operation is needed. Even if the AC button is not turned "on", the system programming will activate AC compressor use when certain external and cabin conditions exist.
NOTE: The manual states that there is a "condensation sensor" in the system; page 139 bottom of left side, in the "AUTO program" section.

Auto mode will attempt to reach and maintain the driver set cabin temp.
This means that under certain conditions the AC compressor will activate even if the temperature setting is set to minimum
For example, you may have the temp set to 65F. The ambient temp is 62F, and humidity is 80%.
In these conditions the HVAC may need to activate heat, but there is a chance that condensation will form on the windshield.
So even though the heater core will allow coolant flow to warm it up, the AC will activate in order to dehumidify the warming air.

I don't use AUTO mode yet I still find some AUTO functions going on.
Even if I shut the AC off, the HVAC will continue to blow cooled air for a good while until it finally stops.
IOW AC doesn't shut off when I shut it off while in manual mode. AC function will continue, sometimes for 5 minutes longer and more. Some of that is likely residual cooling from the material BMW uses in the HVAC ducts. This material cools as the cold air is running around and past it. Then, when the car stops at a light and auto stop/start shuts the engine off the HVAC continues to blow cool air that is cooled by that material. It's a quite interesting set up.

However, many times if I shut the AC off like 5 minutes before I shut my car off and park in the garage, the next time I turn the car back on, like the next morning, the AC will turn on and blow cold air for a while until it finally stops. IOW, the AC compressor kicks in when I fire the cold engine up the next morning and the system will blow cold air for over 5 minutes at times before it finally stops. It's like I shut the system off too quickly after turning the AC off and the computer still hasn't had enough time to run through some "shut down" cycle, so in the morning it activates the AC until it finally shuts off at some point.
Very odd really. If I were in AUTO mode, then I could understand some of that oddity, but I only use manual mode.


If the AC coming on were only humidity related, then it should come on on every humid day, but it doesn't.
I do note that I don't use auto mode for the HVAC. So in auto mode some things could be different.

Just like most things in modern computer controlled cars the switches are simply for asking/telling the computer what you want and then the computer will decide when to actually do it.
Too much computer control on every thing in modern cars imo.
This is why I am not happy with manufacturers moving to drive by wire braking and steering. DBW throttle is ok as long as I can still mechanically control the braking, but steering and braking controlled by the computer doesn't put me at ease.
Knowing that computers do have occasional glitches I'm not confident in having the computer control everything. Heck, I can't even turn the AC off exactly when I want it off, imagine pressing the brakes and the computer has a "glitch".
No thanks.