You can test both the ignition switch and the neutral switch by pulling the connector off the trans. I don't have the pin numbers handy, but if you get 12V on Start on one of the purple leads, then the ignition switch is OK. If you jump the purple leads and the strarter turns on start, then the neutral switch has a problem.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe