What was found
RECEIVED AND INSTALLED REPLACEMENT MGT INDICATOR. APPLIED GROUND POWER AND THE UNIT PASSED THE LCD TEST. AFTER ENGINE START THE MGT INDICATED ZERO. AIRCRAFT WAS SHUTDOWN AND I PERFORMED AN MGT INDICATOR FUNCTIONAL CHECK WITH THE BARFIELD TURBINE TEMP TESTER. THE GAUGE WAS DEAD ACCURATE. I PUT EVERYTHING BACK TOGETHER AND WE RAN UP THE AIRCRAFT AGAIN. AFTER A NORMAL BATTERY START THE INDICATOR WOULD READ CORRECTLY AND THEN DROP TO ZERO AT RANDOM INTERVALS (ROUGHLY EVERY 10-15 SECONDS). THE FIRST REPLACEMENT GAUGE HAD SAT ON THE SHELF FOR ABOUT 6 YEARS. THE SECOND REPLACEMENT GAUGE WAS REPAIRED IN APRIL OF THIS YEAR. THIS AIRCRAFT HAD NO MGT INDICATION ISSUES BEFORE REPLACING THIS GAUGE FOR A DIM SCREEN.