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Just replaced my old Bendix Starting Vibrator with a new electronic Magneto Booster. All I can say is WOW! If you have had starting difficulties like I have...had. Don't even give it a second thought. Get it. I think it started on one crank. Maybe less.

To make a painful story short as i can - '68 M20C with O-360-A1D just out of annual, mags had 500hr IRAN, engine runs great on local flight. Then I flew 2 hrs to Hyannis yesterday- no problems at all. I come back this am and try to start, temps in 50s, Starting vibrator box buzzes, battery is strong, starter turns great, but not the slightest hint of combustion going on. I then get it preheated- still won't make any combustion. I have the mechanic come out on a Sunday - he finds no spark being made on bottom plugs. Connections from starting vibrator to left mag are fine, harness and plugs are fine. I suspect a left mag problem caused by the recent IRAN. But then he checks the starter switch, finds multiple loose connections to the switch, tightens them all. It makes spark, starts immediately. But I don't really get what happened here because I don't know the system well enough. My questions- Did the p-lead ground fail to be broken because a loose connection to the starter switch? If so, would it have been possible for the mags to ground unintentionally in flight? I would think the opposite- it would leave you with a hot mag. Anything else I should investigate here? For whatever it's worth, the ignition switch was replaced in the last 10 years, is made by TCM.