Whining noise when fan on ? (Without AC on)

[Geo41e]

Hey guys

Wondering if anybody has had the same experience.

When I turn my fan on, (heat or cold, and with the A/C off) I hear a whining sound that follows my revs, very similar to a worn AC compressor bearing.

However, when I switch the A/C on, the whining noise goes away ?

Also, if I turn the fan off, the whining goes away.

Is the A/C compressor engaged even if the A/C is not switched on, like an "eco" mode ?

Cheers

[suitedcboy]

The compressor is a variable displacement type and turns continuously. The swashplate that pushes pistons up and down in the axial bores can be controlled to change its angle and bring piston stroke down to 2-3 mm. When a/c is on the swashplate is angle to give piston stroke of 40mm or so maximum and is controlled based on evaporator temperature. The belt pulley has a bearing as normal but BMW does not use a clutch, they have a rubber damper connecting pulley to compressor shaft. I have replaced compressors for noise but the pitch and volume of the noise was dependent on ambient temp and fan speed. The most typical noise "issue" with these compressors is a whizzing that is dependent on compressor load. The noise is louder when car is hot inside and fan speed higher as that is when piston stroke is controlled to greatest stroke and compressor discharge pressure is highest. Electric cooling fans can get a whizzing noise but the cooling fan speed is not related to engine speed. This needs some more diagnosis to know the cause with certainty.

[Geo41e]

Mate, awesome reply and feedback !

so my fan speed is on 1 bar, no AC, desired temp 20-23 C, and ambient temp is around 18 - 20c. even if i match ambient and desirted temps with no ac and fan on 1 bar synced, i still get the whizz matching my revs.

Goes away as soon as i turn it off. If i turn on AC, it goes away..but there is a slight hum as per usual compressor noise.. ?

[ooshnoo]

My F32 does the same thing. Drives me crazy. If you find a solution, please share!

[menohuman]

had the same noise, turned out to be low freon

[Geo41e]

Originally Posted by menohuman

had the same noise, turned out to be low freon

oh really ?

I'll give that a try.

Shes getting a full service in the next few weeks (just picked her up about 3 - 4 weeks ago)

I'll let em know and report back cheers

[james92se]

Originally Posted by Geo41e

Hey guys

Wondering if anybody has had the same experience.

When I turn my fan on, (heat or cold, and with the A/C off) I hear a whining sound that follows my revs, very similar to a worn AC compressor bearing.

However, when I switch the A/C on, the whining noise goes away ?

Also, if I turn the fan off, the whining goes away.

Is the A/C compressor engaged even if the A/C is not switched on, like an "eco" mode ?

Cheers

Are you sure this isn't just belt noise?

Originally Posted by suitedcboy

The compressor is a variable displacement type and turns continuously. The swashplate that pushes pistons up and down in the axial bores can be controlled to change its angle and bring piston stroke down to 2-3 mm. When a/c is on the swashplate is angle to give piston stroke of 40mm or so maximum and is controlled based on evaporator temperature. The belt pulley has a bearing as normal but BMW does not use a clutch, they have a rubber damper connecting pulley to compressor shaft. I have replaced compressors for noise but the pitch and volume of the noise was dependent on ambient temp and fan speed. The most typical noise "issue" with these compressors is a whizzing that is dependent on compressor load. The noise is louder when car is hot inside and fan speed higher as that is when piston stroke is controlled to greatest stroke and compressor discharge pressure is highest. Electric cooling fans can get a whizzing noise but the cooling fan speed is not related to engine speed. This needs some more diagnosis to know the cause with certainty.

The F15 sDrive 35i absolutely has a compressor clutch. I know, because I had to replace it 2 years ago. Was not a fun job.

[Geo41e]

Hey James.

If it were belt noise, the sound goes away with ac on...

I'm curious if the ac compressor is "semi" engaged when the fan is on, but ac off, that would explain maybe slight tension on the compressor bearings/pully?

It's a real odd one

[james92se]

Originally Posted by Geo41e

Hey James.

If it were belt noise, the sound goes away with ac on...

I'm curious if the ac compressor is "semi" engaged when the fan is on, but ac off, that would explain maybe slight tension on the compressor bearings/pully?

It's a real odd one

Generally yes, but not necessarily and not always. I have had a couple of cars over the years whose belts squealed like a pig except for when the AC compressor was engaged.

When I had to replace the compressor clutch/coil a couple of years ago I did notice some unexpected things when testing with the multimeter.

Basically, anytime the HVAC panel is "lit up" - even with the AC button OFF - the clutch is engaged. My testing showed 10-11 volts at the clutch with the HVAC unit on and AC button OFF but I'm not sure if this *should* be enough voltage to lock the clutch, though evidently it is at least in my example - it seems to only be disengaged when the entire HVAC unit is turned OFF (aka no lights or anything on).

[Geo41e]

Originally Posted by james92se

Generally yes, but not necessarily and not always. I have had a couple of cars over the years whose belts squealed like a pig except for when the AC compressor was engaged.

When I had to replace the compressor clutch/coil a couple of years ago I did notice some unexpected things when testing with the multimeter.

Basically, anytime the HVAC panel is "lit up" - even with the AC button OFF - the clutch is engaged. My testing showed 10-11 volts at the clutch with the HVAC unit on and AC button OFF but I'm not sure if this *should* be enough voltage to lock the clutch, though evidently it is at least in my example - it seems to only be disengaged when the entire HVAC unit is turned OFF (aka no lights or anything on).

That totally makes sense based on what you said.

HVAC on, with a/c button OFF, but you are getting voltage from the compressor/clutch...so that would mean mean (in my terms or what not) that HVAC is running on "eco" mode...

with your test, would you say the clutch is somewhat causing "drag" on the compressor/enough tension to turn the compressor ?

Would be good to know if this is the norm from BMW ?
Anywho - hasn't been doing it the last few days.
Note: Last few days, ambient temps are around 10c - 15c, and the HVAC is set to 22c with no AC on... clutch is dictated by HVAC temps if AC off maybe ?