I believe the blower motor connection is in the passenger compartment on the driver's side of the console. If you apply voltage to the two wires at the connector, the motor should run at full speed. If so, the pushbutton unit is dead.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!