INSTRUCTOR WITH STUDENT HAS ALTERNATOR PROB ON APCH; TURNS OFF STROBES AND LNDG LIGHT ON APCH.

Narrative

I WAS CONDUCTING AN INST COMPETENCY CHK WITH A STUDENT. MY STUDENT AND I WERE ON AN INST FLT PLAN FROM TAMIAMI ARPT IN MIAMI TO PALM BEACH INTL. WE HAD PLANNED ON SHOOTING THE VOR RWY 15 APCH AT PALM BEACH COUNTY ARPT; GOING MISSED AND THEN SHOOTING FULL APCH AT PBI WITH A FULL STOP. DURING THE ENRTE PHASE OF THE FLT; THE AMMETER WAS INDICATING A DISCHARGE. I THEN RECYCLED THE MASTER SWITCH TO BRING THE ALTERNATOR BACK ON LINE. APPROX 5-10 MINS LATER; THE PROB RECURRED. I THEN RECYCLED THE MASTER SWITCH A SECOND TIME. JUST BEFORE BEING CLRED FOR THE VOR RWY 15 APCH AT LNA THE PROB OCCURRED A THIRD TIME; PROMPTING US TO MAKE A FULL STOP LNDG AT LNA TO INVESTIGATE THE PROB. I THEN MINIMIZED THE ELECTRICAL LOAD BY TURNING OFF THE LNDG LIGHT AS WELL AS THE STROBES DURING THE APCH. AFTER LNDG WE BEGAN TO TAXI TOWARD THE MAIN RAMP. WE THEN NOTICED A W PALM BEACH SHERIFF'S OFFICER WITH HIS LIGHTS ON AHEAD OF US AND OFF TO THE L APPROX 3-400 FT. AS WE APCHED HIM; THEY JUMPED OUT OF THEIR PATROL CAR WAVING A LARGE GUN AND YELLING TO GET OUT OF THE ACFT. WITHIN 20 MINS; WE WERE SURROUNDED BY 14 POLICE OFFICERS; 10 PATROL CARS; AND A HELI AS THEY QUESTIONED US ABOUT DRUG SMUGGLING BECAUSE WE CAME IN WITH MINIMAL LIGHTING. I FEEL TO PREVENT FUTURE PROBS SIMILAR TO THIS; LCL POLICE FORCES LOCATED IN AREAS WHERE DRUG SMUGGLING IS COMMON SHOULD TRAIN THEIR OFFICERS ON ARPT OPS.