I would trace the voltage along your electrical lines. Do you get voltage at the plug which connects to the blower? If not, do you get voltage at the part before that? That's how I troubleshooted my non-working blower-- traced the voltage. After replacing a mechanically dead switch, I confirmed voltage to the plug that goes into my blower. Replaced the blower and all was good.

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1982 240D 4spd, 327,000mi