'91 500 SL - Blower Motor Inoperative at High Speed Setting
'91 500 SL (R129), 55K miles... ACC blower motor no longer operates at high speed...works fine in first three speed settings, with no abnormal noises; just no high speed.
I understand the blower motor regulators are problematic for the W140, but what about the R129? Correct regulator for this vehicle is #129 821 33 51, which lists for over $525.
How does one differentiate between a failed regulator vs. a faulty blower motor? Hate to buy a part I don't need.
BTW, where is the regulator located on this vehicle?