A C210 pilot diverted because of a low voltage alert after takeoff and executed a go-around following an IMC RNAV approach because he was not stabilized. A voltage regulator and two alternators changers were needed to correct the electrical problem.

Narrative

After takeoff during my climb out; I experienced a low voltage indicator light. I asked to level at 7;000 FT to assess the issue. I was able to reset the alternator and continue on; however; the low voltage appeared again; so I began reducing the draw on the alternator by turning off one radio; the ventilation fan; the strobe lights; the autopilot and the PFD. I also requested that I be able to turn off the transponder; but center said I could only do that for 5 minutes; so I decided to leave it on since I believed that it drew very low voltage. I was able to reset the alternator; but requested that I divert to a nearby airport where I could have the intermittent problem assessed by a Mechanic. I chose that airport because it had good repair facilities and the alternator that had been replaced three weeks earlier had come from an overhaul facility in that city. The airport was reporting IFR when I arrived and I was told to expect an RNAV XX approach. I loaded the RNAV XX approach with the expectation that I would get vectors to the approach. When I was handed off to the Tower they gave me a direct route to the initial approach fix for the RNAV XX approach. I didn't understand the name of the fix and ask the Controller for the name; so I could add it to the flight plan. While reprogramming the approach I descended below the request minimum 3;000 FT altitude until reaching the initial fix; so I began climbing back to that altitude. I lowered my gear and turned on the PFD and autopilot and the low voltage light appeared again. At this point I decide to ignore it since I had no indication of a low battery. While on final approach the Tower asked me to report the base of the clouds which I did when I broke out at 1;500 FT. As I tracked inbound to Runway XX I was high on the approach and did not think I could make a landing on Runway XX without an excessive rate of descent so I requested a circling approach. The Controller cleared me for a circling approach to Runway YY and shortly afterward asks that I turn to a southerly heading. As I proceeded south I lost contact with Runway YY when looking east but could see it when I looked west. I was concerned that I would lose view of the airport as required in a circling approach; so I turned back to the west and proceed on a heading of YY; which lined me up for a landing on Runway ZZ. At some point I asked the Controller if he wanted me on a right base to ZZ; but did not receive a response. I proceed on a downwind right base to Runway ZZ and landed. After requesting that I turn to a southerly heading there were no more communications from the Controller until I was on the runway and he requested that I contact Ground Control for taxi instructions. Frankly; I was surprised that the Controller didn't ask me to come to the Tower to discuss my decision to land on Runway ZZ versus Runway YY; but I thought that he must have determined that I had done what I thought was the right thing to do land safely. After landing; I asked to turn right on Taxiway Hotel to discuss FBO option available to me. I then taxied to the FBO. I tried to reset the alternator and it would not reset; so I shut the plane down; turned everything off and restarted to see if the alternator would come back on line; which it didn't. After some work by the maintenance shop; they determined that the voltage regulator had failed; and it was replaced and all ground run-ups resulted in satisfactory operation of the charging system. They thought that maybe having to reset the voltage regulator a number of times caused it to fail completely when I added a heavy load when landing. However; on departure I experienced a problem similar to the prior problem and returned to the airport for further review. They did more work and determined that there was also an intermittent problem with the alternator which was verified by the overhaul shop. The alternator was replaced and all ground run-ups resulted in satisfactory operation of the charging system. However; on departure the problem still existed and the maintenance shop is continuing to work on the problem. In talking with a number of maintenance people around the country; it appears that there is a quality problem with alternators these days; with several people saying they have had to install 2 or 3 alternators before getting one that works properly. Some have also said the same about voltage regulators. The voltage regulator was replaced again today and ground checks have been satisfactory but we are waiting on improved weather to test fly the plane. I think that the above comments cover the chain of events. The major human performance considerations relate to my preparation for and work load during the instrument approach. I should have reduced my work load by either asking for radar vectors to the approach; since that is the procedure I had loaded; or asking what initial fix to expect when I was told to expect an RNAV XX approach. Having to reprogram the approach distracted my attention to altitude control and delayed my restarting the autopilot and PFD; which in turn distracted my attention in managing my final descent rate; resulting in a high missed approach and request to circle for the approach. Not expecting to have to circle to Runway YY; I had not given adequate consideration to the flight pattern that I should expect from the Controller and when I lost sight of the approach end of Runway YY I decided the safest way to maintain visual contact with the runway environment was to turn to a heading of YY and land on Runway ZZ. In short; my planning and work load during the approach led to me getting behind on executing the several details of the approach and landing but the approach and landing was controlled and safely executed. After dealing with the maintenance problem for two days I finally had a chance to think through the events and called the Tower to discuss what had happened. The Controller who was on duty during my approach was not available but I reviewed the events with another senior Controller and he said that while the controllers always want the pilots to follow their instructions; that the pilot ultimately has to do what he thinks is the safest; and the controllers will monitor the flight and provide advice if they think there is a problem. He also said that he thought that if the Controller had thought there was a problem he would have contacted me in the air or on the ground after landing. While this is some consolation that I did the right thing in following a safe course of action; it is still disappointing that my planning for the approach and potential alternatives for dealing with a missed or circling approach were not sufficient to enable me to comply with the Controller's instructions. Lessons learned; or reinforced; thoroughly plan ahead; consider all possible endings on the approach and initiate actions early so that you can stay ahead of the flight as it proceeds.