Narrative:

While on an IFR flight plan between ryv and fsd had received clearance to proceed direct frm. About 30 NM east found that I could hear ZMP but was unable to respond. Thought it might be a bad microphone so tried a headset I had along, no better. About that time noticed that the VOR receiver had now flagged. Now, looking for something more serious noticed the ammeter at zero. Tried turning off electrical equipment and resetting alternator to no avail. Decided at that point to remain VFR and look for the first available airport which was sbu. Spiraled down and landed there. Immediately phoned FSS so they could cancel my IFR. At lower altitude during the approach into sbu the alternator did reset and started changing again but felt committed to landing and canceling as still unable to raise ATC. After landing ran the aircraft up and all functioned correctly so flew to FOD VFR to have the closest available mechanic look over. To top off a bad day realized that I inadvertently had left 7600 in transponder for about the first 15 NM of that journey. Later discovered the reason for the alternator problem was a short in the battery between 2 cells that showed up only at higher altitudes. I probably should have included the ammeter in my scan during flight to catch this problem sooner. A poor design of the PA28 annunciator contributed since the glareshield obstructs it for taller pilots and it's not bright enough to show up in sunlight. Think I'll keep pleasure flying to a minimum from now on.

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Original NASA ASRS Text

Title: ACFT EQUIP PROB. ALTERNATOR FAILURE LOST COM. RPTR DIVERTED TO THE CLOSEST ARPT TO LAND AFTER EXPERIENCING COM FAILURE. WHILE DIVERTING RPTR WAS ABLE TO RESET THE ALTERNATOR, BUT LANDED ANYWAY IN ORDER TO CHK THE ALTERNATOR PROB AS WELL AS CLOSE OUT HIS IFR FLT PLAN. AFTER DEPARTING, RPTR REALIZED HE STILL HAD 7600 SET IN THE XPONDER.

Narrative: WHILE ON AN IFR FLT PLAN BTWN RYV AND FSD HAD RECEIVED CLRNC TO PROCEED DIRECT FRM. ABOUT 30 NM E FOUND THAT I COULD HEAR ZMP BUT WAS UNABLE TO RESPOND. THOUGHT IT MIGHT BE A BAD MIKE SO TRIED A HEADSET I HAD ALONG, NO BETTER. ABOUT THAT TIME NOTICED THAT THE VOR RECEIVER HAD NOW FLAGGED. NOW, LOOKING FOR SOMETHING MORE SERIOUS NOTICED THE AMMETER AT ZERO. TRIED TURNING OFF ELECTRICAL EQUIP AND RESETTING ALTERNATOR TO NO AVAIL. DECIDED AT THAT POINT TO REMAIN VFR AND LOOK FOR THE FIRST AVAILABLE ARPT WHICH WAS SBU. SPIRALED DOWN AND LANDED THERE. IMMEDIATELY PHONED FSS SO THEY COULD CANCEL MY IFR. AT LOWER ALT DURING THE APCH INTO SBU THE ALTERNATOR DID RESET AND STARTED CHANGING AGAIN BUT FELT COMMITTED TO LNDG AND CANCELING AS STILL UNABLE TO RAISE ATC. AFTER LNDG RAN THE ACFT UP AND ALL FUNCTIONED CORRECTLY SO FLEW TO FOD VFR TO HAVE THE CLOSEST AVAILABLE MECH LOOK OVER. TO TOP OFF A BAD DAY REALIZED THAT I INADVERTENTLY HAD LEFT 7600 IN XPONDER FOR ABOUT THE FIRST 15 NM OF THAT JOURNEY. LATER DISCOVERED THE REASON FOR THE ALTERNATOR PROB WAS A SHORT IN THE BATTERY BTWN 2 CELLS THAT SHOWED UP ONLY AT HIGHER ALTS. I PROBABLY SHOULD HAVE INCLUDED THE AMMETER IN MY SCAN DURING FLT TO CATCH THIS PROB SOONER. A POOR DESIGN OF THE PA28 ANNUNCIATOR CONTRIBUTED SINCE THE GLARESHIELD OBSTRUCTS IT FOR TALLER PLTS AND IT'S NOT BRIGHT ENOUGH TO SHOW UP IN SUNLIGHT. THINK I'LL KEEP PLEASURE FLYING TO A MINIMUM FROM NOW ON.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.