ehopkins, look in your Owner's Manual to see if there are positive and negative terminals under the hood for the purpose of jump starting your 1992 300SE. Our 1998 E320 is equipped that way because the battery is under the rear seat. The positive terminal is enclosed in a black plastic box with a red "+" on the top, while the negative terminal is exposed and has several brown ground wires connected to it. The terminals are side by side on the driver's side.

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Fred Hoelzle