AN ACR B737 FLC EXPERIENCES AN ELECTRICAL FAULT ON BUS #1. THEY WERE ABLE TO RESTORE PWR TO BUS #2 AND USED THE AUX PWR UNIT AS A BACKUP SOURCE.

Narrative

ON A FLT (B737-400) FROM ISP TO PBI; CLBING THROUGH 34000 FT FOR 35000 FT; LOSS OF BOTH GENERATOR BUSSES OCCURRED. THE CAPT BECAME THE PF AND WE REFERRED TO THE ACFT CHKLIST. THE GENERATOR BUS #2 WAS RESTORED BY DESELECTING GENERATOR BUS #1. ALL ELECTRICAL WAS RESTORED; EXCEPT WHAT WAS ON GENERATOR BUS #1. AFTER STARTING THE APU; IT WAS SELECTED FOR GENERATOR BUS #1. LOSS OF BOTH GENERATOR BUSSES OCCURRED AGAIN. DESELECTING THE APU; GENERATOR BUS #2 CAME BACK ON LINE. AFTER CALLING DISPATCH AND DISCUSSING OUR OPTIONS; WE CONTINUED TO PROCEED TO PBI. THE #2 GENERATOR WAS POWERING ALL ELECTRICAL (EXCEPT GENERATOR BUS #1); WITHOUT EXCESS LOAD OR TEMP. THERE WAS NO NEED TO DIVERT SINCE ALL STANDBY PWR AND BATTERY INDICATIONS WERE NORMAL; PLUS THE APU COULD SUPPLY THE #2 GENERATOR BUS (IF NECESSARY). THE ONLY CHANGE TO OUR FLT WAS THE ROUTING. INSTEAD OF FLYING OVERWATER FROM DIW TO PBI; WE REROUTED ALONG THE COAST. WX WAS VFR ALONG THE RTE TO OUR DEST. FORECAST SHOWERS AT OUR DEST HAD MOVED TO THE S. THE FLT WAS COMPLETED WITHOUT FURTHER INCIDENT. WE SURMISED THAT XFER RELAYS FROM GENERATOR BUS #1 TO XFER BUS #1 WERE DEFECTIVE. ACFT CAPABILITIES ALLOWED GENERATOR BUS #2 AUTO CONNECTION TO XFER BUS #1; WHICH IT DID WITHIN GENERATOR LOAD LIMITS. NO NAV OR OTHER SYS DEGRADATION OCCURRED IN THIS CONFIGN. ONLY REDUNDANT ITEMS ON THE GENERATOR BUS #1 WERE INOP.