C230 AC Blower singing
 

My 2000 C230 AC blower has recently started to sing when turned on. I thought it was a bearing problem but when I removed the blower and ran it with a straight DC source it is quiet all the way from 3 volts to 12 volts. If I hook it up through the Voltage Regulator then it starts to sing. More on the lower speed settings than on the high speeds. If I move the red wire up or down at the regulator the sound changes or disappears. I assume that this is a bad regulator but just want to get some verification before I spend the $175 for another one. Anyone have a similar problem or know how the regulator works to explain what is going wrong with it?

If the sounds are from the center vent it may be low of refrigerant.

Check and post the actual values from the CCU. Engine on and AC at 72f and on auto. Press and hold "Rest" for 5 secs, use auto buttons to toggle screens and post values 1-8.

Thank you for the reply Terry. I have the manual CC and there are no diagnostics built in as ther is no LCD panel. This noise is present with the blower out of the dash. AC and heat work fine just the squeal when the blower is powered through the regulator. I could hold the assembly in my hand and press on the contact or lift the contact and the noise will go away. I took the regulator off of the blower and same result the noise is deffinately coming from the regulator. I just thought it was all solid state and should not buzz internally. The noise is about 6Khz but varies with the speed. My thought was could an overcurrent condition cause the regulator to buzz. If I power the blower from a seperate DC supply from 3 volts to 12 volts the motor is quiet and the current looks ok.

First let me say that I know nothing specifically about your car or this problem. However, from the point of view of electronics I can address your statement about solid state electronics. Electronics can indeed make noise. Especially switching regulator circuits. I do not know what type of regulator is in there but I have seen cases where a capacitor goes bad and will make noise. I am not talking about blower regulators but just regulators in general. Anyway it sounds like you have figured it out yourself: Get a new regulator.