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?

__________________
Dave
88 300E 250K Sold
2000 C230K Totaled @104K
2003 ML320 156K Sold
2009 E350 4Matic Sport 46K Sold
2011 ML350 60K Sold
2014 GLK350 46k Sold
2012 GL450 72K For Sale
2016 E550 Cabriolet 48K Sold
2015 GLK350 114K