What was found
TRU3 SHOWING HIGH AMPS (UP TO 603 AMPS) DURING APU START. TRU3 RETURNED TO NORMAL AFTER APU START. FAINT ELECTRICAL BURNING SMELL NOTED IN COCKPIT. SWAPPED TRU 3 (SN: AAL2000833) AND TRU 2 (SN: AAL2000838) REF AMM 24-31-01 FOR TROUBLESHOOTING. DURING OPS CHECK, TRU3 AMPS SPIKED DURING APU START. ALL TRU OPS CHECK GOOD, REF AMM 24-31-01. C/W RELATED CHECKS PER "UNUSUAL SMELL OF SMOKE OR FUMES OCCURRENCE" PER AMM 21-22-00, NO DEFECTS NOTED. TRU3 SPIKE FOUND TO BE NORMAL DURING APU START PER CHIEF PILOTS.