Ok - I moved the tab over the switch and that isn't right. When I did and turned the AC knob completely CCW it does activate the fan and it also turns on the little green AC light indicating the AC is on - NOT the heater (which is backwards - normally the AC is activated when you turn the AC knob CW and then the green light is supposed to come on).

This did help me realize that I was mistaken in which fan was coming on - the heater fan is NOT coming on - it's actually the AC blower that is working.

I did take the cowl off at the base of the windshield and could reach the heater fan - it spins freely so at least it's not seized.

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE