Hey Guys, ?? This story is under the heading of ya never know.... I headed over to the airport Sunday morning to go take some air shots of my job site. Everything seemed so normal and nonchalant. Taxied to the run up and went through the procedure. Everything was fine in all facets of the instruments. Last thing is to turn the transponder from stand by to mode C. The microair has a low voltage indicator that only shows voltage when it is low. I noticed it was showing something like 8.8v. I revved the throttle a little to see if it climbed out of the red. It didn't. So I went to the screen on the EIS and it was showing something just north of 9v. A little bit baffling since I just started up and did a run up with no indication of low power. I revved here a few more times and it did not budge up or down. The voltage had always reacted instantly with the RPM changes. ?? So it was a no go and I taxied back to the hanger. By the time I had gotten just about back instruments started going off line from low voltage and it even ran a bit rough. Voltage was showing about 7.6v at that point. ?? I put her away and started brain storming a bit. No breakers popped, no smoke, no broken belt, no apparent connections problems. I decided to walk away and take some time to think it through. Just before I left I turned the master back on just to see if anything happened. The battery voltage showed 12.3 and all the instruments and lights were working. Now I'm confused more and starting to hate airplanes. ?? I went back last evening and took all the covers off the front end so no to miss a connection anywhere. I could not find the smoking gun. I turned everything on and had the 12.3v and left it all on for almost 10 min. and it never dropped below 12.0v. I decided to go out and start and see what happened running. It started up right away and was charging with everything close to normal but not quit. It usually would get to 14.1v at a high idle of about 1400 RPM. Now it seemed to struggle to get to 13.6 at 220o RPM which is where I can't keep her from rolling any more. I had a spare brand new JD voltage regulator on the shelf so I decided to swap it out just as a check. and it only would take a few minutes to do. ?? She started right up again and showed some improvement. although I was not quit happy just yet. It was getting 13.9 and would touch on 14v at the 2000 RPM. I went over things again just to make sure I had not missed anything. It was getting cold and dark so I put her away for today. ?? I decided to put her back together this morning and do a test flight late in the day. Which I did do this evening. I did the taxi a bit and went and did the run up. For what ever reason everything was exactly as it should be tonight. At 1400 RPM it was just over 14v and by the time I approached 2000 RPM it was bouncing around 14.2 and 14.3v. I took the flight for just under and hour and there was no sign of anything ever being amiss. In fact she was running great in the cooler temps. ?? So in hind sight the only thing that I can figure is the voltage regulator was going bad. IT may have been in a stage of failure that said maybe I'll work or maybe I won't but I warned ya while You were still on the ground. Fortunately I listened for a change. The regulator was used for about 12 years and sitting for a year before that. It has a solid 900 hours on it and probably a fair amount more with ground run time. I don't know what the life expectancy is for them and I really don't know if there is a way to bench test. But for now it seems to have been the problem or the start of a problem. ?? The one exciting thing for the evening was that she seemed to be running so well and the wind was non-existant, so I set the autopilot for straight and level a 3000' and slowly wound her up. At 3270 rpm i was able to get the fastest flat out speed that N357CJ has ever had. She was able to maintain 185 to 186 mph true for over 5 minutes. I think she was just happy to see me. All this is just food for though guys, hope it helps someone. Joe Horton ?
