new started new ignition switch . turn key to no position motor starts.starter runs with motor

English, please.

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'80 300SD - '83 240D - '00 E55 AMG - '02 G500

Interpreting this as "starter won't disengage". First step is check the wiring at the starter, make sure there is no cross contact at any terminal.

Next suspect would be the ignition switch.

Next would be the solenoid or starter (usu. only replaced together).

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Prost!