What was found
LAX FLIGHT NR 2468: ON TAXI OUT, NR 1 TRU SHOWED NO LOAD. MAIN BATTERY SHOWED BETWEEN A CHARGE OF -18 TO A LOAD OF +15 WITHIN A 15 SECOND SPAN AND CONTINUED TO CYCLE. NO TRU CAUTION LIGHT. PULLED TRU C/B PER MTC AND RESET. NR 1 TRU LOAD SHOWED .01 THEN 0. MAIN BATTERY CONTINUED CHARGE/DISCHARGE CYCLE. AIRCRAFT RETURNED TO BLOCK. MAINTENANCE REMOVED MAIN BATTERY FOR FOM. CLEANED CONTACTS ON SHUNTS 2431-R3, 2431-R4 AND 2431-R7. REINSTALLED MAIN BATTERY. GROUND RAN BOTH ENGINES. NO DEFECTS NOTED. NO PARTS REPLACED. AIRCRAFT RETURNED TO SERVICE.