A CRJ200 WAS FLOWN WITH THE #2 ESSENTIAL BUS TRANSFORMER RECTIFIER OPERATING INTERMITTENTLY AND INDICATING 100 AMPS. THE SYSTEM HAD A HISTORY OF WRITE-UPS.

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DURING PREFLT; NOTED THE ESS TRU 2 WAS INDICATING A DRAW OF 100 AMPS. THIS WAS DENOTED IN WHITE AS THIS WAS THE UPPER LIMITATION FOR A TRU. MAINT WAS SUMMONED. THEY FOUND A BLOWN FUSE; REPLACED IT; EVERYTHING APPEARED NORMAL; THEY SIGNED OFF THE ACFT AND WE DEPARTED. I MONITORED THE ELECTRIC SYNOPTIC PAGES AND NOTED THAT THE DRAW ON #2 ESS TRU WAS ABOUT 24 AMPS (A BIT HIGH). I ALSO NOTED THAT THE MAIN BATTERY WAS SHOWING 33 AMPS. AFTER CAREFULLY REVIEWING THE LOGBOOK; NOTED THE FUSE HAD ALREADY BEEN REPLACED SEVERAL TIMES. IN EACH CASE; THE #2 ESS TRU WAS INDICATING 100 AMPS. IN ONE CASE; THE MAIN BATTERY WAS NOTED TO INDICATE 33 AMPS. I WONDERED IF SOMETHING WAS SHORTED THAT WAS CAUSING THE HIGH DRAW INDICATIONS. I CHKED THE DC SYNOPTIC PAGE BEFORE STARTING THE APCH AND I SAW A DRAW ON #2 ESS TRU OF ABOUT 20 AMPS. AFTER LNDG; IT WAS BACK AT 100 AMPS. WHILE TALKING WITH MAINT CTL; I CHKED THE ESS TRU 2 FUSES -- ONE WAS BLOWN AND THE OTHER'S CONTAINER STARTED TO ROTATE WHEN I TRIED TO UNCAP IT SO I LEFT IT ALONE. MAINT CTL HAD ME PULL THE CIRCUIT BREAKER WHICH PROVIDES POWER TO ESS TRU #2 (CBP2-A8). THE ESS TRU THEN TURNED YELLOW; AN ESS TRU CAUTION MESSAGE WAS POSTED. AFTER A MINUTE OR SO THE AMPS STARTED COUNTING DOWN; PAUSING AROUND 20. AFTER A FEW MORE MINUTES IT WENT TO ZERO THEN WOULD INTERMITTENTLY START COUNTING UP MOMENTARILY. THE FUSES IN QUESTION WERE LABELED AS SHUNTS. SEEMS REASONABLE A BLOWN SHUNT WOULD BE A WARNING MESSAGE. SOMETHING CONCERNING IS THAT AT TIMES THESE SCENARIOS ARE NOT NOTICED UNTIL SOMEONE FLAGS IT ONLINE. SOMETIMES PROBS OCCUR BECAUSE OF SHIFT CHANGES ON EXTENDED MAINT (STEPS MISSED).CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THIS AIRPLANE HAD A PREVIOUS HISTORY OF THE ESSENTIAL #2 TRANSFORMER RECTIFIER INDICATING 100 AMPS; WHICH IS WAY OUT OF LIMITS. THE FIX WAS TO REPLACE THE FUSE THAT WAS FOUND BLOWN. THE FACT THE FUSES OR SHUNTS WERE FOUND OPEN SHOULD HAVE ALERTED SOMEONE IN MAINT CTL; ESPECIALLY WITH THE MAINT HISTORY. WHEN THE AIRPLANE WAS REMOVED FROM SVC FOR SOME IN-DEPTH TROUBLESHOOTING; A CHAFED WIRE WAS FOUND THAT WOULD INTERMITTENTLY BE GROUNDED. THE LOCATION OF THE CHAFED WIRE IS UNKNOWN.