Hi-
As I was parking my 1987 w124 300TD wagon a couple of days ago, a strange high pitched whistle or warning buzzer began going off inside the passenger compartment. The noise was coming from the passenger side of the car and started on its own with no changes to any controls or knobs. It ended when I turned off the car. It is loudest inside the car and is not coming from the engine.

I drove the car again just now, and the buzzing/whistling is still going. It is high pitched, and the pitch changes randomly and occasionally briefly stops. It sounds like an old shortwave radio trying to tune in a far-off station. I think it is related to the HVAC system, perhaps a fan bearing or vacuum pod failing.

I tried to record the noise with my cheap-o flip cell phone, but it is hard to hear it well. You kind of have to turn the sound all the way up on your computer and then you may barely hear it if your house is quiet. It is much louder and more annoying in person.

Any suggestions on where to start? I am not excited about tearing into the entire dashboard, but the car is relatively unusable with this rather strange noise. Thanks for your suggestions.

Attached Files

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

Bump-ilstiltskin.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

Its the air sampler motor.

000 830 19 08

Take out the glove box and its down and to your right. About 15 minutes to replace.

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68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i

Thanks DieselPaul. That was very helpful. Once one knows the name of it, it is so easy to find previous threads about it. But when I initially searched, I came up empty.

As you said, it is very quick to replace. So I decided to try a few drops of ATF on the motor shaft and hope it wicks into whereever it is needed. I know it is a long shot, but there isn't really any downside to trying. The part is $60 or more online, so I will postpone that purchase as long as possible.

Thanks again. You saved me so much time.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

I just wanted to followup on this thread. 11 months ago, I pulled the air sample motor and lubricated with ATF. So far, the fan has stayed quiet. So for others on a budget, using ATF to quiet the fan is a reasonable solution to buy some time. I will post again if the noise ever comes back. At that point, hopefully economics will allow me to just buy a replacement part.

Thanks again to DieselPaul for quickly solving this one for me.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).