What was found
PILOT NOTED LEFT FUEL QUANTITY INDICATOR WAS UNRELIABLE AND REPORTING LOWER THAN NORMAL. GAUGE SN 1089 WAS REMOVED AND OVERHAULED, GAUGE SN 4739M WAS INSTALLED AND CALIBRATED TO THE A/C PER MM. GAUGE LASTED ONE TRIP BEFORE RESULTING A LIKE PROBLEM. GAUGE WAS SWAPPED LEFT TO RIGHT, IT WAS FOUND TO BE A PROBLEM WITH GAUGE. IT WAS SWAPPED BACK AND MEL`D. GAUGE SN 4739M WAS REMOVED AND GAUGE SN 2570M WAS INSTALLED. GAUGE LASTED 1 TRIP AND FAILED. THE AC WAS MEL`D FOR FLIGHT WITH THE INOPERATIVE GAUGE. SEVERAL CORRODED GROUNDS WERE FOUND TO PLAY A FACTOR. GROUND POINTS AT PROBES WERE CLEANED, AND GAUGE RECALIBRATED TO THE AC AND WORKED. GAUGE FAILED AFTER SECOND FLIGHT AFTER INSPECTION. MAINTENANCE LOOKED A