The buzzing you hear is coming from the throttle body, the throttle body is powered by the OVP. Your car should have either A 000 540 67 45 or A 000 540 52 45 OVP both have white tops. If you use OVP with red top the throttle body does not power off and drains your battery.

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600SEL '91
300E 4Matic '88
240D '83
280SE '77
350SE '73
The most complex systems can fail in the simplest way.
Contra verbosus noli contendere verbis, sermo datur cunctis, animi sapientia paucis.

i don't believe in the lord! He's never bought me a Mercedes Benz.