PA28 PVT PLT SUFFERS A LOSS OF HIS ALTERNATOR BUT DELAYS IN THE RECOGNITION OF HIS PROB. AFTER DEALING WITH THAT; HE RUNS INTO A PROB USING HIS GPS WHICH IS NOW ON BATTERY PWR.

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ON FEB/SUN/97; I FLEW WITH 2 PAX FROM LWM TO RKD ON A SIGHT-SEEING FLT. DURING THE TRAINING FLT; COM #1 HAD SOME AUDIO DISTORTION; AND WHAT SEEMED TO BE A MARGINAL SQUELCH SETTING. I USED COM #2 AS MY PRIMARY RADIO FOR THE FLT. WE WERE USING A BATTERY-PWRED INTERCOM FOR THE PLT AND BOTH PAX. I WAS USING A YOKE-MOUNTED VFR GPS (GARMIN 195). THE GPS WAS RUNNING ON A CIGARETTE-LIGHTER PLUG INTERFACE TO THE ACFT ELECTRICAL SYS; WITH ITS INTERNAL RECHARGEABLE BATTERY AS BACKUP. THE BATTERY WAS FULLY CHARGED AT THE START OF THE DAY; IT HAS A 7 HR LIFE-SPAN WITH NO BACK-LIGHT. I HAD A HAND-HELD RADIO (ICOM ICA-21) IN MY FLT BAG. IT STARTED THE DAY WITH A FULLY CHARGED BATTERY AS WELL. THE FLT NORTHWARD COMMENCED AT XY30 LCL; AND WAS UNEVENTFUL EXCEPT FOR THE #1 COM RADIO ACTING UP. WE LANDED. ON THE SBOUND FLT AT 4500 FT MSL; NAV WAS VISUAL; VOR AND GPS. WE WERE RECEIVING ADVISORIES FROM ATC; WERE SQUAWKING A CODE AND WERE IN CONTACT WITH BRUNSWICK; PORTLAND; AND MANCHESTER APCH CTLRS. OUR ELECTRICAL FAILURE OCCURRED WHILE WE WERE IN CONTACT WITH MANCHESTER APCH 125.05. WE WERE FLYING INTO A SUNSET; AND IT WAS OBVIOUS THAT THE LNDG WAS GOING TO EFFECTIVELY BE A NIGHT LNDG. THE SBOUND FLT PROCEEDED NORMALLY UNTIL FAILURE OF RADIO #1 LESS THAN 20 MI N OF PSM. THE DISPLAY BEGAN FLASHING ERRATICALLY; I CONCLUDED THAT #1 RADIO FAILED. I SHUT OFF RADIO #1. MANCHESTER APCH RPTED LOSS OF MY SQUAWK; AND REQUESTED THAT I RECYCLE MY XPONDER. I NOTICED THAT THE LIGHT ON THE XPONDER HAD BEEN REMAINING ON SOLIDLY; AND IT WAS DIM. UPON RECYCLING THE XPONDER; MANCHESTER APCH STILL DID NOT RECEIVE MY SQUAWK. IT WAS AT THIS TIME THAT RADIO #2 FAILED IN EXACTLY THE SAME WAY AS #1. I TURNED OFF RADIO #2. I TURNED TOWARD PSM WHICH WAS IN SIGHT AND AT ABOUT 4 MI. I SET MY XPONDER FOR 7600 AND PRESSED IDENT. NO LIGHT CAME ON AND I REALIZED THAT THE XPONDER WAS OUT. IT WAS THEN THAT I CHKED THE ALTERNATOR (GENERATOR?) METER FOR CHARGING CURRENT AND IT READ ZERO. I INTERPRETED THIS AS AN ALTERNATOR FAILURE; AND REALIZED THAT WE HAD ONLY BATTERY PWR LEFT. I TURNED OFF ALL ELECTRICALS EXCEPT THE TAIL STROBE. I ASKED MY WIFE; WHO WAS IN THE BACK SEAT TO GIVE ME THE HAND-HELD RADIO. I TRIED CALLING MANCHESTER APCH ON 125.05; BUT RECEIVED NO RESPONSE. I WAS ALMOST ON TOP OF PSM AT 4500 FT MSL AT THIS POINT; SO I CALLED PSM TWR; AND ASKED THEM TO RELAY MY SIT TO APCH. I CONCLUDED THAT THERE WAS EFFECTIVELY NO DIFFERENCE IN SAFETY LNDG AT PSM OR LNDG AT LWM ABOUT 12 MINS AWAY. I INFORMED MANCHESTER APCH OF MY INTENTIONS; AND THEY ASKED TO BE INFORMED WHEN I SWITCHED TO LWM TWR FREQ. AT THIS TIME; I LOOKED DOWN AT MY GPS WHICH WAS ON THE HSI DISPLAY PAGE. THE WAYPOINT IT WAS NAVING TO WAS LWM; WHICH IS CORRECT FOR LAWRENCE ARPT. IT INDICATED A GND TRACK REQUIRED OF ABOUT 240 DEGS. I TURNED DIRECTLY TOWARD THE WAYPOINT AND PRESSED 'GOTO' AND 'ENTER' TO CREATE A NEW RADIAL TO THE WAYPOINT. THE DEFAULT WAYPOINT IN THE GOTO SCREEN IS THE CURRENT GOTO WAYPOINT; THIS IS A QUICK WAY TO RESET THE COURSE LINE. CREATING THE NEW RADIAL RE- CTRED THE NEEDLE; AND I BEGAN CAREFULLY NAVING DIRECTLY TO LWM. I USED A FEATURE OF THE GARMIN 195 WHICH GIVES VERT NAV INFO; AND BEGAN A DSCNT OF 500 FPM BASED UPON GPS INFO. I THOUGHT I HAD IDENTED THE ARPT VICINITY AT 12 O'CLOCK; BUT THIS LATER TURNED OUT TO BE ROCKINGHAM PARK; A RACETRACK. I LATER REALIZED THAT THIS DECISION-MAKING PROCESS ALONG WITH THE NAVIGATIONAL ISSUES CAUSED ME TO NOT COMPLETE MY FULL LNDG CHKLIST. I LANDED WITHOUT THE MIXTURE IN THE FULL RICH POS. THIS WAS A PROCEDURAL ERROR ON MY PART. THE HSI SCREEN OF THE GPS WAS GIVING ME ERRONEOUS INFO; BUT THE MAP SCREEN WAS CORRECT. I REALIZED THAT THE HSI DISPLAY WAS STEERING ME ON A PARALLEL TRACK; BUT 5.6 MI TO THE R (NW) OF THE CORRECT COURSE. I REMEMBER THAT WHEN I SWITCHED TO THE MAP DISPLAY; I LOOKED FOR THE LUBBER LINE ON THE STRIP COMPASS. ON THE GARMIN 195; THE LUBBER LINE ALWAYS INDICATES THE GND TRACK TO THE CURRENT WAYPOINT. THE LUBBER LINE WAS NOWHERE TO BE SEEN; EVEN THOUGH THE HSI DISPLAY INDICATED MY WAYPOINT WAS DEAD AHEAD. I BELIEVE THAT THERE IS A SOFTWARE BUG IN THE GARMIN 195 (SOFTWARE VERSION 2.01) SPECIFICALLY RELATED TO THE HSI DISPLAY. I VISUALLY PICKED UP THE ARPT OFF THE L WING AND TURNED TO ENTER A WIDE DOWNWIND FOR RWY 32 AT LWM. I ANNOUNCED MY TURN TO FINAL ON THE HAND-HELD. THE LWM TWR CTLR (CTLR #1) CLRED THE OTHER ACFT FOR DEP. THIS WAS A NIGHT LNDG AND ONE WITH A COMPLETE ELECTRICAL FAILURE. I THINK IT WOULD HAVE BEEN PRUDENT TO HOLD UP THE ACFT ON THE GND UNTIL I WAS DOWN AND OUT OF THE PATTERN. I HAD NOT DECLARED AN EMER. I STARTED THE FLT WITH 3 LEVELS OF NAV: VISUAL; GPS; VOR. AFTER THE ELECTRICAL SYS FAILURE; I SEEMED TO GET 'TUNNEL VISION' ON THE GPS; EFFECTIVELY ELIMINATING ANY XCHK WITH MY VISUAL NAV. I THINK CTLR #2 HAD A HARD TIME JUDGING MY DISTANCE WHEN I WAS ON FINAL APCH. I HAD ONLY A TAIL STROBE VISIBLE. THE A&P MECH VERIFIED THAT I HAD EXPERIENCED A VOLTAGE REGULATOR FAILURE. THE ALTERNATOR ITSELF WAS REBUILT WITHIN THE LAST YR. GARMIN VERIFIED THAT THEIR SOFTWARE UPDATES (THEY ARE UP TO 2.04; MY UNIT WAS 2.01) HAD CORRECTED BUGS IN THE HSI DISPLAY. I HAVE NOT RECEIVED THE UNIT BACK FROM GARMIN AS OF THIS WRITING.