Non working Blower Fix
 

I accidently found something anybody experiencing an intermittant Blower Motor should know.
Try repositioning the ignition key slightly when the blower motor cuts out or when it won't function. I have seen this happen on 3 different MB's and the "jiggling" method of the key worked in all 3 cases.
I think there's a fine line in the ignition switch that allows the play over time to cut out the electrical power to the blower motor.
Try it if it happens, you have nothing to lose and then you'll be one step closer to the real culprit.

Kip
95 SL500
88 300E