Haven't been able to crawl underneath to check the grounding strap, but I did get a voltmeter and checked battery voltage. With engine off, I read 12.6 V, started engine and read 13.1 at idle. Turned on lights, got about 12.9 , with AC about 12.5 (idle) 12.9 at 2000 RPM.

Do these voltages seem right?

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1989 300E
103,500 miles

1982 300SD
Sold but not forgotten