Originally Posted by cdplayer

I am not familiar with this model. But I have removed and inspected many blowers and related parts to the W201 and W126 chassis.
The noise you are hearing, IMHO, is not the regulator. No moving parts that I know of. If your car has one, the noise is coming from the aspirator(air sample blower). This small blower takes air samples from inside the car and blows them over a room temp sensor.
In the W201, the aspirator is located behind the passenger vent. In the W126, it is behind or under the glove box.
Over time, the blower get very dirty. The bearings dry out and thus the squeal. If you locate yours and remove it, test the fan blades. They should spin freely with very little effort. If not, apply a thin oil to the bearings and test with 12V. You may be able to recover.
I have a box full of these little blowers I sell on Ebay.
The pic attached is what you may be looking for.