Narrative:

I was giving the last dual night flight to a student pilot. After takeoff the lights started to dim. I was about 20 mi from our airport, practicing lndgs at an airport which is normally class D, yet closed at XX00PM and was now class east down to 700 ft AGL. After the lights started to dim I asked the student if he had turned them down, he replied 'no.' I then took over the controls and started to check the amp meter, it indicated 0 charge or discharge. I tried recycling the master, tried just running on the battery, then just the alternator. No response. During this time I had made a broken, partial contact with kalamazoo approach, they replied that they were not receiving my transponder. I decided to turn back to the uncontrolled airport where I knew there was very little to no traffic (in kalamazoo there was numerous traffic, and I also had no way of indicating that I needed light gun signals). I went back to battle creek, I was trying to isolate the problem without any success. I took out the poh and followed the procedures which ended with landing as soon as practical. At this point I lost all electrical. I went downwind, base, final. On final, with my student holding our flashlight on the airspeed indicator, the lights on the runway went to almost completely off. I then did my best in my attempt to land and taxi off. I thought that the lights on the runway went completely off, yet I had no way to turn them back on. After repairs were made on the airplane, it was found that the voltage regulator had failed.

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Original NASA ASRS Text

Title: DIVERSION TO ALTERNATE REQUIRED IN A NIGHT OP WHEN A C- 172 HAS A PRIMARY ELECTRICAL SUPPLY PROB.

Narrative: I WAS GIVING THE LAST DUAL NIGHT FLT TO A STUDENT PLT. AFTER TKOF THE LIGHTS STARTED TO DIM. I WAS ABOUT 20 MI FROM OUR ARPT, PRACTICING LNDGS AT AN ARPT WHICH IS NORMALLY CLASS D, YET CLOSED AT XX00PM AND WAS NOW CLASS E DOWN TO 700 FT AGL. AFTER THE LIGHTS STARTED TO DIM I ASKED THE STUDENT IF HE HAD TURNED THEM DOWN, HE REPLIED 'NO.' I THEN TOOK OVER THE CTLS AND STARTED TO CHK THE AMP METER, IT INDICATED 0 CHARGE OR DISCHARGE. I TRIED RECYCLING THE MASTER, TRIED JUST RUNNING ON THE BATTERY, THEN JUST THE ALTERNATOR. NO RESPONSE. DURING THIS TIME I HAD MADE A BROKEN, PARTIAL CONTACT WITH KALAMAZOO APCH, THEY REPLIED THAT THEY WERE NOT RECEIVING MY XPONDER. I DECIDED TO TURN BACK TO THE UNCTLED ARPT WHERE I KNEW THERE WAS VERY LITTLE TO NO TFC (IN KALAMAZOO THERE WAS NUMEROUS TFC, AND I ALSO HAD NO WAY OF INDICATING THAT I NEEDED LIGHT GUN SIGNALS). I WENT BACK TO BATTLE CREEK, I WAS TRYING TO ISOLATE THE PROB WITHOUT ANY SUCCESS. I TOOK OUT THE POH AND FOLLOWED THE PROCS WHICH ENDED WITH LNDG AS SOON AS PRACTICAL. AT THIS POINT I LOST ALL ELECTRICAL. I WENT DOWNWIND, BASE, FINAL. ON FINAL, WITH MY STUDENT HOLDING OUR FLASHLIGHT ON THE AIRSPD INDICATOR, THE LIGHTS ON THE RWY WENT TO ALMOST COMPLETELY OFF. I THEN DID MY BEST IN MY ATTEMPT TO LAND AND TAXI OFF. I THOUGHT THAT THE LIGHTS ON THE RWY WENT COMPLETELY OFF, YET I HAD NO WAY TO TURN THEM BACK ON. AFTER REPAIRS WERE MADE ON THE AIRPLANE, IT WAS FOUND THAT THE VOLTAGE REGULATOR HAD FAILED.

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.