FOLLOWING UNUSUAL PREFLT CHECK OR RUDDER TRIM; CAPT OF MD80 PREVAILS UPON MAINT FOR COMPREHENSIVE TROUBLESHOOTING.

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WHILE PRE-FLIGHTING THE AIRPLANE I HEARD A DISTINCT SOUND; SOMEWHAT SIMILAR TO A SOCKET WRENCH RATCHET RETURNING. THIS SOUND START IMMEDIATELY AS SOON AS I STARTED TURNING THE RUDDER TRIM KNOB AND IT CONTINUED UNTIL I REACHED 7 UNITS OF R RUDDER TRIM. AFTER PASSING 7 UNITS OF R TRIM; THE NOISE SUBSIDED AND DID NOT RETURN WHEN I WAS CHKING THE TRIM; ALTHOUGH IT DID RETURN LATER IN THE DAY WITH SEVERAL DIFFERENT MECHS CHKING THE TRIM. THE TRIM OPERATED SMOOTHLY; FULL TRAVEL FROM STOP-TO-STOP WITH NO STIFFNESS OR BINDING NOTED. MY MAJOR CONCERN WAS OVER WHAT CAUSED THE INITIAL NOISE WE HEARD AND WOULD THE CAUSE OF THE NOISE EVENTUALLY CAUSE TROUBLE IN THE NORMAL OP OF THE RUDDER TRIM. MAINT WAS SUMMONED AND AN ENTRY WITH THE MAINT DISCREPANCY WAS ENTERED INTO THE MAINT LOGBOOK. INITIALLY THE LCL MECH DIDN'T ACT AS IF HE WANTED TO WORK THE PROB AND THEN HE GOT MAINT CTL INVOLVED. MAINT CTL DECIDED TO SIGN OFF THE LOGBOOK DISCREPANCY SINCE THERE WAS NO PRIOR HISTORY WITHIN THE PAST 30 DAYS AND SINCE THEY WERE NOT ABLE TO DUPLICATE THE NOISE WE HEARD. I WAS NOT HAPPY WITH THIS COURSE OF ACTION AS WE STILL HAD NOT ANSWERED THE QUESTION OF WHAT CAUSED THE NOISE AND WHY WAS THE NOISE PRESENT IN THE FIRST PLACE. AFTER I EXPRESSED MY CONCERNS; MAINT MUST HAVE DECIDED THE PRUDENT THING TO DO WOULD BE TO TROUBLESHOOT IN HOPES OF LEARNING WHAT WAS CAUSING THE NOISE WE HAD ONCE HEARD. THE PLANE WAS OTS FOR NEARLY 12 HRS BEFORE MAINT DISCOVERED THE SOURCE OF THE NOISE. TURNS OUT THERE WAS A BUNDLE OF CAPPED AND DISCONNECTED WIRES (FROM THE AUX FUEL TANKS I'M ASSUMING) THAT HAD COME UNTIED AND THEY WERE RUBBING AGAINST PARTS OF THE RUDDER TRIM AS IT TURNED. MY MAJOR CONCERN IS THAT WHEN A WRITE-UP IS ENTERED ON A FLT CTL PROB SUCH AS THE RUDDER TRIM; MAINT SHOULD ALWAYS DO A THOROUGH TROUBLESHOOT UNTIL THE SOURCE OF THE PROB IS POSITIVELY IDENTED AND CORRECTED. WE CAN'T AFFORD TO TAKE CHANCES WITH FLT CTL PROBS. MAINT NEEDS TO PROPERLY TROUBLESHOOT WHEN A MAINT DISCREPANCY IS ENTERED INTO THE MAINT LOG RATHER THAN JUST SIGNING IT OFF WITH NO TROUBLESHOOT.