Greetings,

I cannot control fan speed on the A/C control unit on my 95 wagon (78k miles). Every other button/ function works fine.

The control unit itself works fine since I removed it and switched it in to my E500. Similarly, the E500 unit did not operate fan speed in the wagon. All 94/94 W124s use the same control unit, as verified by Bosch part number.

Clearly the issue is something else. Can anyone help please!

Thanks
farrukh

That car like most newer MB's has an electronic blower control unit. ON the W124 chassis it is mounted below the blower motor.
IT receives info from the pushbutton & varies the speed of the blower by controling how much ground goes to the motor.

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MB Doc, thanks for your note.

How would I diagnose if it is the motor which has malfunctioned and therefore caused the regulator to fail, or whether it is just the regulator which has failed.

Thanks in advance for your help.
farrukh