AFTER TROUBLE-SHOOTING AN ACFT EQUIP PROB MALFUNCTION AND RESOLVING THE ISSUE OF THE GEAR PROB; LTT ACR LANDS AND THEN DEPARTS WITHOUT SOLVING THE CAUSE OF PROB WHICH HAD RESOLVED ITSELF. FAA INTERESTED IN AIRLINE MGMNT POLICY PROC.

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THE FLC WAS MAKING A SCHEDULED PART 135 FLT FROM ORD TO SBN. THIS WAS THE SECOND LEG OF THE DAY AND THE CAPT WAS FLYING. ON DSCNT WE EXTENDED THE LNDG GEAR IN A NORMAL FASHION AND WHEN WE HEARD THE GEAR LOCK WE NOTICED THERE WAS ONLY THE SOUND OF THE GEAR LOCKING AND NO DOWN LIGHTS (NO 3 GREEN LIGHTS). AT THAT TIME I ASKED THE SBN TWR IF WE COULD TURN E TO 'DO A FEW CHKS.' WITH APPROVAL; WE PROCEEDED E AND CALLED OPS AND TOLD THEM TO CALL MAINT. AT THAT TIME WE CALLED OPS AT SBN AND RELAYED TO THEM WHAT STEPS WE HAD TAKEN. AT THAT TIME THE CAPT LOOKED BACK AT THE GEAR INDICATOR LIGHTS AND THEY WERE ILLUMINATED (ON). WE THEN RELAYED ALL THIS INFO TO ONE OF THE COMPANY'S PLTS ON THE GND AT SBN. HE TOLD MAINT AND THEY SAID THE GEAR MUST BE DOWN. WE THEN DECIDED THAT SINCE WE COULD SEE THE 2 MAIN GEAR AND THEY APPEARED TO BE DOWN AND WE COULD SEE THE REFLECTION OF THE NOSE GEAR IN THE SPINNER WE HAD DONE ALL THE CHKS AND THEY ALL SAID THE GEAR WAS DOWN AND WE NOW HAD 3 GREEN; WE WOULD RETURN TO SBN TO LAND. WE TOLD APCH WE WERE READY TO RETURN. THEY GAVE US TO SBN TWR. WE THEN REQUESTED A LOW PASS TO HAVE THEM LOOK AT THE GEAR. THEY SAID THE GEAR APPEARED TO BE DOWN SO WE RETURNED TO LAND ON RWY 27. AFTER LNDG WE TRIED TO DUPLICATE THE PROB AND WERE UNABLE. WE THEN TOLD COMPANY MAINT THAT WE WERE UNABLE TO DUPLICATE THE PROB. THEY SAID TO CONTINUE THE DAY'S FLT SO WE PROCEEDED BACK TO ORD THEN TO SBN AGAIN AND ON RETURN TO ORD AGAIN WE DISCOVERED THE PROB WAS IN THE INTERIOR LIGHT DIMMING SWITCH. WE THEN WROTE THE PROB UP IN THE MEL AND TRADED THE AIRPLANE TO ANOTHER CREW. THE TWR AT SBN; AFTER WE TOLD THEM WE NEEDED TO DO THE CHKS; CALLED THE SBN FSDO WHO SENT AN INSPECTOR TO OUR OPS OFFICE TO INQUIRE ABOUT THE EVENT BUT BY THE TIME HE ARRIVED WE HAD ALREADY DEPARTED TO ORD. CONCERNED THAT WE HAD DEPARTED TO ORD WITH A BROKEN AIRPLANE HE CALLED THE DSM FSDO AND RPTED THIS TO OUR 'PMI' WHO CALLED OUR DIRECTOR OF MAINT. HE THEN INFORMED HIM OF THE EVENTS AND OF HOW THE PROB WAS INTERMITTENT AND UNABLE TO DUPLICATE.