Notorious W124 "Phantom Drainers"

1.Antenna
2.Trunk Light switch AND the "Flex" point at which the Trunk hinge impinges
on the Wiring Itself.
3.A bad diode in the Rectifier Bridge of the Alternator.

If it drains a healthy battery overnight it's a Big Drain (s).
I'm gonna throw out a WAG since I don't know the schematics of your chassis's
wiring diagram...It's an UnFused "Hot At All Times" user.

Invest in an inexpensive DMM from Sears or HF.
You need to know how bad the Amperage Drain is .

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'84 300SD sold
124.128