A buzzing part that has no name (yet.) - PeachParts Mercedes-Benz Forum

ardnews · #1 08-17-2004, 05:42 PM

My 1989 560 SEL has a very irritating buzz coming from under the right side dash. I took the underside panel off, exposing the small part that is making the constant noise. It is wrapped in about 1/4 inch of insulation. It includes a silver box about the size of a pack of cigarettes. A small fan (maybe an inch in diameter) is coming out of its side and blowing into either a hose or cable that then leads up the wall and into the bowels of the upper dash.

This buzzing part sits about 9 inches above the Engine Control Module. In fact, until I really pinpointed it I suspected the ECM was buzzing.

There is an electrical plug that enters the box on the opposite side from the fan. It apparently can be unplugged, but until I know what it does I will not do that. I will just continue to turn the CD player up higher until I can fix it.

The buzz starts when I turn the key on accessories and continues once I start the car.

I have a shop manual on CD but I have not found this part. I have looked on all sorts of parts catalogues and have not seen this part.

Please help me ID this mystery part and tell me is it essential. If not, I will remove it until I can buy and install a replacement. Otherwise, I will drive in ignorance.

400E · #2 08-18-2004, 08:16 AM

Sounds like the aspirator fan. It sucks air from a foam tube, which in turn goes up the "A" pillar and into the courtesy light assembly near the rear-view mirror. There is a thermistor under a grill in the courtesy light assembly which provides feedback to the climate control system. The purpose of the aspirator is to ensure a constant sampling of cabin air temperature.

If you shut off your climate control while the buzzing is occuring, the buzzing should stop if it's the aspirator.

If it is the aspirator, it eventually should be fixed or replaced. If it isn't working properly, the climate control system tends to act erratically.

ardnews · #3 08-18-2004, 03:02 PM

Now that I know what it is, I have disconnected it until I can get a replacement "sampler blower." The silver insulated box, apparently designed to keep the noise down, disguised the part for me. Now that I took it out I can see that it is a part that I've seen in a catalogue.

Thanks for the quick response. The ride is much quieter now and I can turn the music down.

Q · #4 08-18-2004, 03:20 PM

Try lubricating the thing through the fan opening. I used TriFlo and it worked great. No more buzzing. Don't use anything like WD-40. That stuff will make it worse over time. Machine oil or 3-in-1 oil will work great too.