What was found
AT TOP OF DESCENT, LEVEL FLIGHT, BOTH MAIN FUEL GUAGES READ 3.9 . AFTER PITCHING DOWN, DURING DESCENT, THE LEFT FUEL GUAGE READ 3.1 AFTER LEVEL OFF THE LEFT FUEL GUAGE, READ 3.9 AGAIN, MATCHING THE RIGHT FOR REMAINDER OF THE FLIGHT. GROUNDED - YES. REMOVED & REPLACED NR 1 MAIN FUEL TANK COMPENSATOR, PROBES NR 1, 2, 3, 4, 5, & 6, 7,8, 9, 10, 11 & 12 IAW AMM 28-41-21/401. ACCOMPLISHED TANK UNIT CAPACITANCE CHECK IAW AMM 28-41-21-710-801. ACCOMPLISHED FQIS OPS TEST IAW AMM 28-41-00-710-801. OPS CHECKED GOOD. ACCOMPLISHED FQIS SYSTEM TEST IAW AMM 28-41-00-730-801. ALL READINGS ARE WITHIN LIMITS. GROUND VERIFICATION SUCCESSFUL.