Found my battery dead this am.... Battery took a charge and started, but voltage is showing only 12.2 volts while driving at cigarette lighter plug.... usually was 13 plus. Battery tested OK at local shop, but they couldn't test alternator because the Autozone tech didn't know how to get a tach reading on a diesel!!! (no plug wires to attach to).

How do I test the alternator?

What else shoul I check?

Thanks...

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Mr Goodfahrt (pronounced FAIRT... means "good trip" in German)

1982 300D Turbo Pastel Gray (off-white) 200k+(?)
newbie but willing