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defrost blows hot vents blow cold

20K views 13 replies 10 participants last post by  mohow 
#1 ·
a new HVAC problem here...when set on auto at my standard 70 degree setting the defrost vents on the dash all blow warm air as expected on a 40 degree day but all the upper vents are blowing cold air. even if I turn the temp dials up to 80 and adjust the air temp in Idrive for the hotter setting, the air is ice cold from the vents and hot on the upper defrost vents. Any ideas? I've kept my HVAC settings the same for the last 2 years so I noticed this problem immediately.
Thanks!
 
#2 ·
Go to 'Vent Setting' in the Climate section on your idrive and check the temperature for the center vents (setting between the - and + signs). It probably has one or more blue bars as opposed to the red. Center vent temps are independent of the temperature knob setting. Love this feature since it lets me blows slightly cold air on my face while keeping the car warm.
 
#4 ·
I should have mentioned this in my original post but I'm very familiar with the vent settings in Idrive and all vents are set to blow warm air. And it's been cold here for weeks so if it was related to the vent settings I would have noticed it awhile ago. This was a situation where yesterday morning, while on "auto" all vents blew warm air - Got in the car to leave work later in the day and all vents blew cold except defrost which blew warm.

I've done a fair amount of searching and most of what I've found has to do with all vents blowing cold not this situation where the defrost vents still deliver warm air
 
#5 ·
i have something similar where during hot summer days w A/C blowing, it blows scalding hot air into the footwell.
I have not been able to solve it so far.
I know there are some regulator switches for each vent area, and it is computer controlled. Thought one of them needed replacing, but then one day i noticed the little side vents in the upper dash were also blowing hot air. The ones that point towards the side windows.
I had same issue with my old e39 and was never able to solve it.

Have tried diagnosing with Autologic, but nothing comes up.
I am living with it for now as it is colder outside, but at some point I need to leave the car with a genius who can figure this out.
 
#7 ·
No, but now in winter I don't mind.
Will look into it again in spring.
 
#8 ·
Bump. Anyone ever solve this? My face vents blow cold while the feet and defrost blow HOT. Idrive settings, auto/manual don't change anything.

Another (probably) separate problem is I only get hot on the highest temp setting so it's as if my blend doors need recalibration.
 
#11 ·
try turning the fan speed down for a few seconds, then press Auto when you feel cold air. The system keeps the cold air recirculating if it is not cold enough, which may be due to a tired compressor. Give it a try. If it still doesn't push cold air you may need to top off Freon. Could be a leak.
 
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