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Discussion Starter #1 (Edited)
I noticed that my fan speed was not fluctuating. Seems that when the fan speed is on auto it stuck at 4 bars. I can manually run it up and down but when I press auto it goes back to 4. I also noticed that my max does not work. Pushing it does nothing. Light does not come on and nothing changes.

Did some research and it seem the FSU is the most likely cause for weird climate control issues. Replaced it but no difference.

Whats next? Maybe an interior temp sensor?

Should also mention that my exterior temp sensor is bad. I don't know how this would be related and its been broke for over 6 months.
 

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Discussion Starter #3
Yes your exterior temperature sensor will cause your auto and max buttons not to work.
Well it drive me a little crazy that it says -40 so I guess I will get a new one and see what happens. It won't be a waste like buying the FSU.

I played with it some more and found that its not stuck at 4 bars but it won't go over 50% even if I set it to 60 or 90. I was used to getting full fan speed when the car sat in the sun.

scan tool tells me my aux water pump is faulty. Will look at that I guess as well.
 

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Well, you have got me thinking I may have a problem I didn't know I had. Mine does the same - no matter how hot or cold the interior is, the fan speed stays fixed in AUTO at whatever I set it at. I had a '72 Buick that used to vary the fan speed automatically so it surprised me the M5 didn't.

My exterior temp sensor works fine, so that's not the reason. But I do have the same code for a bad aux. water pump. I have not bothered to fix it because the pump didn't seem to do anything significant. Maybe it does.

But first, my question is should the fan speed vary up and down automatically when in AUTO mode?

EDIT: I searched and the answer is yes, the speed should change automatically. Now, why doesn't it?
 

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Discussion Starter #5
Well, you have got me thinking I may have a problem I didn't know I had. Mine does the same - no matter how hot or cold the interior is, the fan speed stays fixed in AUTO at whatever I set it at. I had a '72 Buick that used to vary the fan speed automatically so it surprised me the M5 didn't.

My exterior temp sensor works fine, so that's not the reason. But I do have the same code for a bad aux. water pump. I have not bothered to fix it because the pump didn't seem to do anything significant. Maybe it does.

But first, my question is should the fan speed vary up and down automatically when in AUTO mode?

EDIT: I searched and the answer is yes, the speed should change automatically. Now, why doesn't it?
So you found the auto has two function, if the light is on it controls where the air comes out. If it says auto by the fan speed then it should also control the fan speed.

the final stage unit (FSU) is a common failure point. You tube it, you will find it easy to replace. Takes all of 2 minutes. This however didn't fix my issue. Waiting for my exterior temp sensor to come in and will see if that changes anything for me.
 

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Jeez, thank you, man! Now it works! I didn't realize if you change the fan speed manually, you have to hit the AUTO button again to get the AUTO text beside the fan speed to get it back to automatic. I've lived with this for three years! Live and learn.
 

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Discussion Starter #8
got my new $7.00 outside temp sensor and climate control appear to be working like it should. MAX now works and the auto button has much more range over the fan speed.

Not sure why the car would all of a sudden start caring about a sensor that has been reading -40 for almost a year now, but whatever. Its fixed.

now to change the secondary pump, not a $7.00 part and by the looks of it is going to cause a radiator flush.
 

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Not sure why the car would all of a sudden start caring about a sensor that has been reading -40 for almost a year now, but whatever. Its fixed.
I don't know why it worked at all with a broken temp sensor. If the car thinks it's -40 outside and you want it 72 inside it makes sense that it's not going to start blowing cold air.
 

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I don't know why it worked at all with a broken temp sensor. If the car thinks it's -40 outside and you want it 72 inside it makes sense that it's not going to start blowing cold air.
It will. You just have to do it manually. Max and Auto won't work. Unfortunately I've broken my outside air temp sensor twice due to poor placement of it by BMW making for easy contact with bad driveways and such. It's currently at -40 and I have the replacement parts to fix it again this weekend but my AC will blow cold as long as I set it manually. I just can't use the Max or Auto functions with it like this.
 

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I've never been sure if my auto AC actually works correctly because I don't understand how it works. It never seems to turn off of max fan speed so I just manually control it. I remember reading in the manual that it tries to achieve your target temp as quickly as possible, which I assume means blowing out at max fan speed, but I find that incredibly annoying. And what exactly does the little manual hot/cold dial at the top by the vents do? That thing + digital temp control makes no sense.
 

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The dial at the top vents is for fine tuning of the temp out of those vents. If you have the AC on and that set on red believe it or not you will get heat out of there.
 
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