What was found
FLIGHT DIRECTOR SYS NOTED INOPERATIVE DURING TAXI FOR TAKEOFF. AVIONICS WERE SHUTDOWN & TURNED BACK ON WHICH DID NOT CORRECT THE PROBLEM. AVIONICS HAD BEEN ON FOR CLOSE TO AN HOUR PRIOR TO TAXI. AVIONIC BAY DOORS WERE OPENED TO COOL SUSPECTED OVERHEATED UNITS WHICH DID CORRECT THE PROBLEM. ACFT FLEW TO TWO DESTINATIONS WITH NO ISSUES. AFTER ACFT RETURNED TO HOME BASE AVIONICS WERE DETERMINED TO BE OPERATING NORMALLY. FLIGHT GUIDANCE COMPUTERS, AVIONICS J BOXES & SYMBOL GENERATORS WERE REMOVED, PINS CLEANED & RE-INSTALLED. SATISFACTORILY OPERATED AVIONICS FOR OVER 1 HOUR. IT IS BELIEVED HEAT, ALONG WITH RESIDUE ON PINS CREATED THIS INCIDENT. CREWS ARE REQUESTED NOT TO OPERATE AVIONICS UNNECESSARILY ON THE GND FOR PROLONGED PERIODS.