I have a face-lifted W212 and I've never observed the blower motor running when the car is off? I'll have to check mine, next time I turn the car off the with the A/C on I'll return in 20 minutes and see if the blower is running.

I'm also a long-time W124 owner and I'm very, very familiar with the HVAC system on this series mainly due to having to fix it so damn much. When its working correctly its world-class in all respects but the number of failure points (vacuum pods, aspirator motors and tubes, vacuum lines, vacuum control blocks, blower regulators, control control valves) on the W124/W123 and W201 series cars is just mind-blowing. The transition to variable displacement A/C compressors in the later cars was a real game changer, much more efficient and easier on the mechanical bits as instead of the full-on/full-off clutches of the earlier designs. I tried to use my mityvac a couple of weeks ago and found it inoperative after sitting in the case for 7-8 years. In my W123/W124 days it seems like I was using it at least every other month to diagnose vacuum leaks.

In stark contrast I know absolutely nothing about the HVAC controls in any post W202 series car I've owned because I've never had any problems with the control circuitry. Pure guess on my part but I'd guess MB used way fewer vacuum controlled devices on later control systems.

I really like the way the W212 manages the blower speeds in the AUTO setting, the fan kicks in high-speed and then drops off as the cabin cools/heats. I've also noticed the HVAC system seems to communicate with the engine management systems to enhance cooling performance. When I start the car after its been in the sun a couple of hours and the interior is 140+F the transmission shifts at higher RPM's until the cabin cools off. It appears the me that the engine management system uses higher engine speeds to enhance compressor performance. Pretty clever.

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