Unless you cannot risk it due to high crime area, you can take the switch out and carefully use a screwdriver or needlenose pliers to start the car while you wait for the replacement switch.

DO NOT WAIT. Get the tumbler out before it totally fails. At a minimum, take it out now for an inspection. Mine is one of the posts pasted above -- the one which fell into 4 pieces as it came out, so my 'inspection' was rather telling.

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David
1986 300E Anthracite + ECodes + MB Mileage Award