08-12-2019, 06:37 PM | #1 |
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AC turns on even with button off
Anyone ever notice the AC turning on when you don't want it to?
I personally drive around with it off a lot because it ruins shifting. But it seems to come on even when the AC button is off. So I have to turn off the fans which I don't like to do.
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08-12-2019, 09:28 PM | #3 |
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On mine, if I start the engine with the AC set to off it stays off. Once I turn the AC on I have found only two ways to turn it off and have it stay off - set the temperature setting to about two degrees above the outside temperature, or turn off and restart the engine. The first can be uncomfortable and the second can be inconvenient.
Were you following this forum during the air conditioning wars of about a year ago? If not, be warned that some people here can get pretty huffy when someone says they want the AC off. Many of them mod their cars endlessly but when it comes to AC "BMW engineers are omnipotent". The fact that the manual makes it clear that off and auto are both acceptable seems to make no difference to them. I think the fact that BMW makes it so hard to keep the AC off simply means that the engineers think most people are too inattentive to dry out the HVAC properly after they use the AC, but no one really knows.
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08-13-2019, 06:07 AM | #4 |
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How does the AC ruin shifting? Just curious, though I don't shift anymore, at least consciously.
And how would I dry out the HVAC properly? I have owned half a dozen BMWs in the last 20 years and always leave the AC on auto all the time, the way God intended. None of them has had a problem with HVAC (yet!!). |
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08-13-2019, 09:22 AM | #5 |
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I have had this occur too. I read somewhere recently that the F30 has a humidity sensor that turns on the AC regardless of the button. F22 is probably the same.
at the end of a long trip, I like to run the air on high with the AC off just to evacuate all the cold air. helps over the long term by keeping any condensation from forming. at least thats the theory. this HVAC system is over complicated I think. E30 was perfect in ease of use, simplicity, and number of options. IMHO anyway. engine speed changes when the AC is running. how fast it speeds up and slows down. gotta slightly change how fast or slow you shift. experienced MT driver's do it without thinking. cars these days have enough power where it barely noticeable. in lower powered cars like my E30, there is a huge difference. yes, my E30 had AC, lol.
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08-13-2019, 10:56 AM | #6 |
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try to put HVAC on manual mode, direct the air flow to panel vent or floor vent only.
(No air directed to windshield) Then turn off AC with AC button. It should stay off this way. Auto HVAC can run AC compressor for defog operation. (regardless of the AC on/off) |
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08-18-2019, 06:56 PM | #7 |
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Same happens with my m240. I even coded the AC not to automatically come on in Auto mode, still it comes on even if the AC light is off. I notice it happens when I start the car up and shuts off after about 5min.
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08-19-2019, 05:30 AM | #8 |
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The 5 minute run on startup sounds right. This would dry out the ducts and coils. This is probably a misguided nanny.
Not all the world is as humid as the Fatherland. |
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08-19-2019, 08:38 AM | #9 |
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Air con definitely will come on by itself in these cars.
Case in point: Last week was pretty nice (weather-wise), so the top was down and therefor no need for the air con. Saturday I had to go into Toronto on an errand and it was cool but misty and rainy. 10 minutes into my drive, I felt cold air hitting my face - the air con had come on by itself. The windows weren't fogged up, but I assume the air con sensors must had hit some humidity threshold. The air con stayed on for the remainder of the trip. BTW, no lights showed up which would indicate that the air con was on.
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08-19-2019, 01:17 PM | #10 |
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A work around for me is to let the AC run for a good couple minutes, then turn it off manually.
I'm guessing once the AC is engaged it may need to run a few cycles before the system can manually shutting down. |
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08-20-2019, 09:19 PM | #11 |
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So must be a humidity thing. Glad I'm not the only one going crazy
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08-21-2019, 07:35 AM | #13 |
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Apparently, this is the new normal; it happen to me in a brand new X2 loaner, It didn't freak me out, it seems like it had a purpose..
There is similar thread in the M4 forum: Fan still on for few minutes after ignition is turned off https://f80.bimmerpost.com/forums/sh....php?t=1614290 |
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11-20-2021, 03:49 AM | #14 |
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Hi all,
Thanks a lot to all of you.. God i`ve searched for this for some time... I have an F30 335dx and from time to time, especially when it rains.. the AC turns on by itself while the AC button is off.. It driven me crazy..i thought it was something with the AC compressor.. and when i saw the price from BMW.. omg ) Thanks! |
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11-20-2021, 12:17 PM | #16 |
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The AC is not just to cool the air, it also functions as a dehumidifier. My AC runs all winter long, even (especially) when it is -30C out. The AC dries the air, and the heater heats it. Keeps the windows from fogging up. Many years ago I operated a truck plow and air conditioning was a huge benefit in keeping the windows clear.
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11-20-2021, 01:42 PM | #17 | |
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11-20-2021, 01:43 PM | #18 | |
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11-20-2021, 04:33 PM | #19 | |
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People smarter than me have decided the former is a better solution, and given interior fogging is pretty much a thing of the past I'm gonna defer to them on that. The latter is how we did it in the old days. Nothing like driving in the winter with your window open. Last edited by Kernel Kurtz; 11-20-2021 at 04:43 PM.. |
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11-20-2021, 05:03 PM | #20 | |
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Running the AC will remove the moisture your breath puts into the air only on recirculation. Try that at -30 and see how clear your windows stay. Have you driven in -30 recently? The only thing some modern cars do better is aim some warm air at the side windows. (And, of course, running the AC just makes that less efficient.) The proportion of cars that are driven routinely at very cold temperatures is so low that engineers don't bother to design the cars to work well then. If they did they would add a button that would turn the AC off. But that would cause far too many problems in humid, warm climates.
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11-20-2021, 05:41 PM | #21 | |
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If I had to choose between recirc with AC or recirc without AC, that is a no brainer of course. I prefer no recirc and AC, that works the best almost always. Perhaps you could try it and report back. And I drive in -30 every winter. I'm quite sure the reason there in no AC off button is not because I don't live in a warm climate and the engineers don't care. We have hot weather and cold weather packages on these cars that encompass many mechanical systems. Pretty sure the button would be easy if it offered any benefit. |
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11-20-2021, 10:18 PM | #22 | |
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As for your understanding of "simple chemistry" (actually it's basic physics), all I can say is WOW! I bow down before a master of self deception.
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