What was found
MAIN FUEL TANK #1 QTY 8.16, CTR 8.00, MAIN TANK #2 8.62 - WITHIN 2 MINUTES #1 QTY 7.59, FUEL BURN AND FLOW NORMAL - XFEED FUEL AND IMBAL LIGHT ON. #1 TANK DID NOT GO OFF UNTIL MAIN TANKS WERE WITHIN 200 LBS. AFTER LANDING, #1 QTY INCREASED 500 LB. GROUNDED - YES. REMOVED AND REPLACED #9 TANK UNIT PROBE REF B737-800 AMM 28-41-21-000/400-801. REMOVED AND REPLACED TANK UNIT #7 ON TANK #1 REF AMM 28-41-21. OPERATIONAL CHECK OF TANK AND COMPENSATOR UNITS GOOD AS WELL AS FQIS OPERATIONAL TEST. LEAK CHECK OF FUEL PANELS GOOD.