What was found
(CAN) THE THREADS OF THE UPPER HORIZONTAL PANEL SUPPORT ATTACHMENT SCREW CHAFING ON AN UNPROTECTED WIRE BUNDLE CAUSING TWO WIRES TO ARC BETWEEN EACH OTHER AND MELTING THE INSULATION. SMOKE NOT REPORTED BY PILOT, BUT WAS NOTED DURING TROUBLESHOOTING. WIRING REPAIRED AND WIRE BUNDLE SPIRAL WRAPPED. SHORTER SCREWS USED TO SECURE PANELING. TWO OTHER AIRCRAFT FOUND WITH SAME PROBLEM.