There is a vacuum switch that will come with the new lock assembly as well as the electrical switch. If you have concerns about being locked out suggest you replace the assembly and swap your new tumbler into it. You won't regret it.
Flying to LA. Gotta go!

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mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)