HVAC fan controls don't work

[Bdc101]

After purchasing our new 2012 35d, we noticed the AC works great but on our second or third trip, we turned it on full blast to cool the car off on a hot day and found that the fan only blew very slowly even when it was turned up to high.



In the following week's we've found that the problem is intermittent. Sometimes the fan responds to the control in the dash, other times no matter what you do it stays at the same speed.



When it's not working, you can turn the fan speed up and down and the HVAC display shows correctly -- it responds to the button push. But the fan never changes speed. The only exception is you can turn the fan off entirely and turn it back on, but when it comes back on it is at the same speed as before. Turning the A/C off and on works correctly during this time, as does the temperature dials.



The rear HVAC suffers from the same intermittent problem. (Our car has 4-zone HVAC.)



I replaced the final stage unit with a new Valeo part today and no change.



I checked codes with my Foxwell the other day and didn't find any, however, at the time the fan was working. I'll check again tonight or tomorrow when it comes back from running errands.



What else might I look into after the FSU? All my searching results have turned up the FSU and nothing else. Thanks in advance.

[andrewwynn]

Use the foxwell to command fan changes. To determine if the head unit is sending the commands.

[Bdc101]

OK, the wife brought the car home so I tried that.



It read a couple of codes about "No Message" in the IHKA2 module. When I reset them, it had no change on the symptoms, and the codes didn't come back.



When I active tested the blower in Foxwell, the only option was to run it at 80%, which it worked correctly when doing that. Then, I read the live data of the blower speed. The live data reported the command I was giving the blower through the HVAC panel, but the blower speed was stuck on one speed all the time.



I did find that pushing the defrost button through the HVAC panel runs the fan at full speed as well. But only on the defrost vents.



Does that tell you anything???

[andrewwynn]

Suggests problem in the control board. Too bad the foxwell doesn't allow more options.

I'd want to wish it's just a bad connection but thread following on xo leans towards replacement panel.

Look though to see if you can change things like temp up/down with the fox. I know I could test most button functions like move steering wheel in/out etc.

[Bdc101]

Foxwell didn't have any other options to test. You think the control panel is the same for a pre-LCI? I found a couple on eBay from pre-LCI cars that look exactly the same.

[andrewwynn]

If you look in real oem I think it shows the date range for each producti id. It will say when a model supersedes another and you can usually figure out from that if they are interchangeable.

[Bdc101]

Looks like a yes as far as I can tell: https://www.realoem.com/bmw/enUS/sho...32#64119227924

[andrewwynn]

Just find the right model number that fits your yes/no for steering wheel control etc I think you'll be good.


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[Bdc101]

Cool -- I double checked it against my VIN options and found one that works. It also comes with the fascia and the lower button strip which I needed anyways because my hatch button is worn off. Will report back!

[andrewwynn]

My backup camera button worn out reminds me I need to get one of those.

I think you can just pull them off to swap.