I'd say that if it solves the problem 100% of the time that it must be the iginition switch itself which is bad. It is odd that it would allow you to start the car but not "turn on" the accessories...but you can't argue with succesfully debugging it the way you did to find a workaround. I'm not sure if you can replace the switch yourself or not...anyone know if this has to be "coded" to the car like so many other parts of the key system?

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz