Symptoms of a bad blower regulator on a W210?
 

My fan will occasionaly slow down and stop on its own. If I turn the fan off for several minutes it usually comes back on when restarted. The AC system works fine as cold air trickles out the vents when the fan is acting up. Is this the dreaded bad blower regulator problem? I have seen threads on how to fix it I just am not sure of the symptoms. TIA

The most typical symptom of a bad regulator is the inability to get higher blower speeds. If the blower stops completely it could be the blower itself or the regulator which is bad. Sometimes a bad blower can be restarted with a firm whack as it re-seats the brushes. You can determine if it is the blower or regulator by monitoring the voltage to the blower when it is acting up. If it is putting out power and the motor isn't turning then you know it is the motor and not the regulator.

FWIW, several other motors in cars with around 200K miles seem to have failed recently...that might be about the average life.

Thanks Marty. Is that voltage one of those that I can monitor with the onboard system?

Its screen 10 IIRC.

Mine (blower motor) acted up as Marty outlined. I could usually fire it up buy reaching under (with panels removed) and giving the squirrel cage fan a quick nudge clockwise. Brushes go out.

What platform? more info?

You can monitor the blower motor voltage using teh CCU while driving around. Press and hold REST for 5 secs. Use L/R AUTO buttons to toggle to the various screens.

If your blower isn't blowing, but regulator voltage is rising when set to auto, you've got bad brushes more than likely.