I have a Series 5 with a 912ULS. A few weeks ago I ran up the engine and did ignition check. Ran fine with ignition A grounded out. Switched and ran real rough on A alone. It runs and sounds fine with both ignitions on. Mechanic has checked both ignition modules, and coils. I have checked all spark plug wires. Someone suggested it might be a bad connection on the ignition switch for A. Will check that out next time at airport. Question, if an ignition module is bad or going bad, does it run at all? Any other ideas would be appreciated. Need to go flying.