My 1985 300D w/ 150K miles...Climate Control System went out. For about 2 days, sometimes it would come on and other times when I restarted the engine, nothing. No air circulates or blows at all on any setting. The couple times in those 2 days it did come on, heat and cool worked strong and perfectly. Now nothing will come on at all.

I checked the clutch on the compressor and when the car starts, the clutch spins and then stops.

I read about replacing blower motor brushes, could this be it? Seems too easy. Would this cause the clutch not to engage?

How do I diagnose the source of the problem...certain steps to take in order?

Thanks.