What was found
FUEL GAGES READ NORMAL AT TAKE OFF BUT CLIMBING THROUGH 5000' FUEL IMBALANCE LIGHT ILLUMINATED - LEFT MAIN TANK INITIALLY READ 1400 LB LOWER THAN THE RIGHT MAIN. THEN LATER ESTABLISHED AT 1000 LB DIFFERENCE. GROUNDED - YES. REF MIG-2C'S AND TASKCARD 78528000 FOR RII AND SAFETY PRECAUTIONS. REF LOG 11757074 ACCOMPLISHED NG-28FCD-18088-1, REMOVED, REPLACED, AND TESTED NR 1 TANK COMPENSATOR, AND TANK UNITS F1, F6, F7, F8, F9, & F10 IAW AMM 28-41-21-000/400-801. ALL TESTS PASS, OK FOR SERVICE. CLEARS MEL 28-12B AND MEL 28-6B.