I believe the resistor is for the aux fan, but the M Benz pros can verify this. It is a big coil in my car also. Probably generates some good heat under load.

I do not know what resides under the battery, but I am pretty sure the leaves can do no good under there.

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1989 560SEL
1971 Cutlass convt. (sold)
1978 Olds Toronado (sold)
the rest are boring