A DH8-Q200 'GEN HOT' CAUTION LIGHT ILLUMINATED. MAINT MEL'ED THE GEN WITH THE GCU OFF. MEL WAS INCORRECT BECAUSE A DAMAGED BEARING WAS DISCOVERED AFTER A SECOND FLT WHEN THE 'GEN HOT' LIGHT AGAIN ILLUMINATED.

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AT TOP OF DSCNT; 75 NM FROM ZZZ1; '#2 GENERATOR HOT' CAUTION ILLUMINATED. CONDUCTED EAC WHICH DIRECTS CREW TO TURN OFF RESPECTIVE GENERATOR. APPROX 10 SECONDS AFTER SHUTTING OFF GENERATOR #2; CAUTION EXTINGUISHED. CALLED MAINT CTLR FROM AIR. UPON ARR; A MECH MET THE AIRPLANE AND ANNOUNCED MAINT'S INTENT OF MEL'ING GENERATOR #2. I IMMEDIATELY WAS HESITANT BECAUSE: 1) MEL IS FOR GCU; WHICH SEEMED TO BE OPERATING NORMALLY UNTIL WE SHUT IT OFF. 2) MEL DIRECTS MAINT TO INSPECT VISUALLY FOR SIGNS OF OVERHEAT (IMPLYING THAT AN OVERHEAT WOULD BE UNACCEPTABLE). WE DIDN'T NEED TO INSPECT. THE CAUTION SYS REVEALED AN OVERHEAT. I RELAYED THIS INFO TO MAINT CTL AND WANTED AN INTERP FROM SOMEONE WITH OPERATIONAL CTL. I REQUESTED DISPATCH HAVE THE DUTY OFFICER CALL ME. THE DUTY OFFICER CALLED. I RELAYED ABOVE CONCERNS AND REQUESTED AN INTERP WHETHER MEL RELIEF WOULD BE LEGAL. DUTY OFFICER ENTHUSIASTICALLY SAID FLT WAS ABSOLUTELY LEGAL BECAUSE: 1) THERE WERE NO VISUAL SIGNS OF OVERHEAT (MEL WORDING) SO STRUCTURAL INTEGRITY WAS INTACT. 2) IF THE GENERATOR CTL WAS SELECTED OFF AND NO FURTHER OVERHEAT WAS DETECTED; THE GCU COULD BE CONSIDERED INOP FOR THE PURPOSE OF THAT MEL. I REQUESTED THAT DUTY OFFICER CONSULT MAINT CTL ABOUT SYS OP AND CALL BACK. WHEN DUTY OFFICER CALLED BACK DUTY OFFICER HAD CONSULTED MAINT CTL AND SAID WE WERE HAVING CONVERSATION ON RECORDED LINE (DUTY OFFICER'S SOLUTION TO REFUSAL TO ADD REMARK ON RELEASE). DUTY OFFICER SAID THAT FLT WOULD BE SAFE AND LEGAL BECAUSE MAINT SAID THAT THE OVERHEAT SENSOR WAS PASSIVELY CONNECTED TO THE GCU. SINCE THE OVERHEAT CAUTION EXTINGUISHED WHEN THE GCU WAS SELECTED OFF; IT INDICATED A MALFUNCTION IN THE GCU WHICH RESULTED IN AN INCORRECT OVERHEAT SIGNAL. WITH THIS INFO IN HAND (AND NO REASON TO DOUBT IT); I ELECTED TO PROCEED TO ZZZ2 AFTER ACFT WAS MEL'ED BY OUTSTATION MECH. AT TOP OF DSCNT INTO ZZZ2; THE #2 DC GENERATOR CAUTION LIGHT ONCE AGAIN ILLUMINATED. WE RAN CHKLIST; BUT NO CREW ACTION WAS TAKEN EVEN THOUGH GCU WAS ALREADY OFF. UNEVENTFUL LNDG. MAINT ELECTED TO CHANGE OUT GENERATOR #2. NOW CURIOUS; I OBSERVED MECH REMOVE GENERATOR AND ASKED HIM IF HE COULD TELL WHETHER THE GENERATOR REALLY WAS RUNNING HOT. HE ATTEMPTED TO TURN GENERATOR ARMATURE WITH LITTLE SUCCESS AND SAID THAT HE THOUGHT THE BEARING IN IT SEEMED TO BE FAILING AND WAS CAUSING EXCESSIVE FRICTION AND HEAT. THIS IS A PROB BECAUSE I NOW BELIEVE THAT THE ACFT SHOULD HAVE BEEN EITHER REPAIRED IN ZZZ1 OR THE GENERATOR REMOVED FROM THE ACCESSORY BOX AND FERRIED. UNCLR WORDING AND INTENT OF MEL; JUDICIOUS INTERP OF MEL LEGALITY BY MAINT CTL AND DUTY OFFICER. POSSIBLY INCORRECT FACTS ABOUT SYS OP RELAYED TO FLT CREW INFLUENCED CREW'S ACCEPTANCE OF MEL FOR THAT FLT. CHANGE MEL TO MORE CLEARLY REFLECT CONDITIONS FOR ITS USE. COMPEL DUTY OFFICERS TO ADD AMENDMENTS TO RELEASES TO REFLECT ULTIMATE RESULT OF DISCUSSIONS ABOUT OPERATIONAL SUITABILITY (AT CAPT'S DISCRETION). ENSURE OPERATIONAL PRESSURES DO NOT INFLUENCE MAINT CTL AND DUTY OFFICER'S INTERPS. MAKE SURE MAINT CTLRS AND DUTY OFFICERS ARE FAMILIAR WITH RESPECTIVE SYS OP BEFORE ISSUING SYS GUIDANCE TO FLT CREWS.