[secretsquirrel]

I've started to notice an odd high pitched squeak when I accelorate slowly when the AC is on. The sound seems like its coming from the left side of the passengers console area (but its hard to pinpoint the exact location). The noise goes away when the AC is off.

Does anyone have a clue of what this could be? I'm in a 07 e90 335 if it matters. Thx

[CoralRed335XI]

I think I have the same problem. Did you ever figure it out?

[mike3000fl]

when you say AC on and off, do you mean the whole AC system? like fan completely off and fan on. Or do you literally mean AC, like the AC snowflake button with the green light??

if the sound goes away while you cycle the snowflake button, it is something probably compressor or belt or tensioner related. if it does it no matter the snowflake button position, but goes away when you turn the fan completely off....

then heres the deal. in that area is the blower motor fan. inside the dash in front of passenger next to glovebox.

you probably have a leak at the bottom of your windshield, where the plastic cowling begins. water seeps down there and ends up in the area below the microfilter. from that compartment the water enters the recirculation vent (directly in front passenger) and runs down into your blower motor, rusting the bearing.

this can be confirmed in a couple ways, after a hard rain, open hood, remove the screws that fold the microfilter cover on, take a flashlight and look around in the area below microfilter for evidence of water. you should be able to see the vent that opens and closes for AC recirc, it has slats. you can also just feel the carpet on the passenger floor for wetness.

either of you had a window replaced recently?

also possible the bearing is just done from natural causes and not water ingress. either way though its the blower motor fan.

see if dealer covers this under warr or cpo. if you had a new windshield go back to your insurance and say it wasnt done right. if neither, you can remove the blower and attempt to lube with a light spray oil lubricant, be prepared for your car to smell interesting the next week or so. it comes out from under the passenger dash, look for a DIY in the DIY forum. not as hard as you would think.

[secretsquirrel]

Originally Posted by mike3000fl

when you say AC on and off, do you mean the whole AC system? like fan completely off and fan on. Or do you literally mean AC, like the AC snowflake button with the green light??

if the sound goes away while you cycle the snowflake button, it is something probably compressor or belt or tensioner related. if it does it no matter the snowflake button position, but goes away when you turn the fan completely off....

then heres the deal. in that area is the blower motor fan. inside the dash in front of passenger next to glovebox.

you probably have a leak at the bottom of your windshield, where the plastic cowling begins. water seeps down there and ends up in the area below the microfilter. from that compartment the water enters the recirculation vent (directly in front passenger) and runs down into your blower motor, rusting the bearing.

this can be confirmed in a couple ways, after a hard rain, open hood, remove the screws that fold the microfilter cover on, take a flashlight and look around in the area below microfilter for evidence of water. you should be able to see the vent that opens and closes for AC recirc, it has slats. you can also just feel the carpet on the passenger floor for wetness.

either of you had a window replaced recently?

also possible the bearing is just done from natural causes and not water ingress. either way though its the blower motor fan.

see if dealer covers this under warr or cpo. if you had a new windshield go back to your insurance and say it wasnt done right. if neither, you can remove the blower and attempt to lube with a light spray oil lubricant, be prepared for your car to smell interesting the next week or so. it comes out from under the passenger dash, look for a DIY in the DIY forum. not as hard as you would think.

I somehow missed this awesome response. Thanks for taking the time to detail this out so thoroughly! I'm going to try to see if I can lube the blower because its annoying. My car is starting to sound like a jalopy between this and my wastegates. I gotta get this under control!

[RoundelM3]

I have the same thing in my early 2007 E92...it's the blower motor, and it seems after a number of years, it develops a "squeak" at certain speeds. I notice it more in the colder months, and especially on really cold days (well, in Central Texas, that's anything under 40 degrees). I will occasionally hear it with the A/C on, and it sometimes does it under acceleration. It's annoying, but my CPO doesn't cover it, and I don't want to tear into it myself. And it's not a constant thing.