Having problems w/ battery going dead. The battery is not the problem. How much current should the car be drawing with the switch off? Could a diode be bad in the alternator? Or something else?

Just a few milliamps. bad diode could explain it. Acid deposits on the top of the battery, trunk light switch stuck on, electrical vacuum pump stuck on, short somewhere.

With the engine off , place a non magnetized steel object on the alternator shaft, it is feels magnetic, your alternator is failing. ( Shorted diode )

Check that the antenna motor is cutting off when it should.

Sixto
83 300SD buy me
98 E320 wagon

search "parasitic drain". More useful info comes up than what will be posted in 1 thread here.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

thanks to all, will start checking

Also check the dome light. There's an electronic board in it that can go flaky and randomly turn the dome light on or off. Mine failed where it would come on in the middle of the night. Would be fine all day, but come out late at night or in the morning and the dome light would be on about half-brightness and pulsing with the seatbelt lights flashing.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)