Air roar when switching between air recirculation modes

[556129]

I noticed this problem slowly progressing in my 02 520i. When the air con is running, and is in recirculation mode, there's a slight roar especially at speeds above 80kmh, which gets progressively louder with higher speeds. However when you r speeding n press the recirculate button and allow the outside air in, there's a sudden zing (frankly it sounds like an F1 car speeding by) sound, like some valve is opening and the roar noise immediately goes away... The roar wasnt there earlier so i suspect it could be perhaps the air cleaner getting dirty. I notice the same issue with my friend's e39 530i, so it appears to be a prevalent problem. Anyone hvng this problem and knows how to resolve this? Sownership experience has been pretty good, with the 520i, with only a gear box adaptation problem and this zinging thing. thanks guys and gong xi fa cai.

 

[moots]

in the e39,whenever the a/c is switced on,the default mode is vent ie. the recirc light on the a/c panel does not light up.when recirc button on the mf steering or on the a/c panel is pressed only will the recirc mode engage.
vent mode - 50/50 air from outside and interior
recirc - valve closes and air inside cabin is reciruculated

if you have lo air flow in vent mode,then most likely your microfilter is clogged.easy to confirm.remove the filters and test,(filters located in the engine bay near bulkhead on the lh n rh side)

 

[bimmerholic]

in the e39,whenever the a/c is switced on,the default mode is vent ie. the recirc light on the a/c panel does not light up.when recirc button on the mf steering or on the a/c panel is pressed only will the recirc mode engage.
vent mode - 50/50 air from outside and interior
recirc - valve closes and air inside cabin is reciruculated

if you have lo air flow in vent mode,then most likely your microfilter is clogged.easy to confirm.remove the filters and test,(filters located in the engine bay near bulkhead on the lh n rh side)

Bro that's not by default i.e (A/C not in recirc mode when switched on). My climate control starts up with whatever settings i had prior to shutdown. If recirc was on before shutting down, it'll start up with recirc. This is called CKM (Car Key Memory) feature. The 1st owner ticked the available list of CKM options when taking delivery of the car from showroom. It can be programmed.

 

[moots]

thanks for the headsup bimmerholic,my input is based on my experience on my car.bmw design philosophy is also basd on safety.generally when we drive,long distance,we should periodically let in fresh air(vent) to avoid drowsiness from the stale air in the cabin when we select recirc (for better a/c temps and disallowing bad outside air).hence the reason why by default,the setting is at vent,to "force" us to have fresh air and after that the consumer decides what to choose.yes this option can be chosen at purchase and reprogrammed by the user as well.
just my 2 sen worth....have a happy chinese new year ushering in the year of the tiger

 

[bimmerholic]

Yup...make sense. Maybe in their country of birth, the air's there fresher and cleaner. Over here until and unless you're climbing up Genting/Cameroon or any other high hilly areas, the air down here is simply polluted and isn't fresh. Well it's different if it's after rain in the night or wee hours in the morning where the air feels so fresh! Love to drive w windows down during these times.

 

[Jerman]

Yup...make sense. Maybe in their country of birth, the air's there fresher and cleaner. Over here until and unless you're climbing up Genting/Cameroon or any other high hilly areas, the air down here is simply polluted and isn't fresh. Well it's different if it's after rain in the night or wee hours in the morning where the air feels so fresh! Love to drive w windows down during these times.

bimmerholic is correct. The recirculation (Open/Close) function is not that practical in our climate conditions. You should just set it by default to CLOSE (always at recirculation mode). Better still, stick a foam at both the air vents (after the microfilters) to prevent outside air from seeping into the cabin. If you do that, you even save the hassle of changing microfilters for life...$$$!
Get the above done at Naidu's (behind Shell station, Jalan Gasing) for less than RM 50.
Malaysia Boleh :top: