As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT CI 346 - DURING COCKPIT PREFLIGHT CHECKS, WHEN MASTER DIM AND TEST SWITCH PLACED TO 'TEST' POSITION, CIRCUIT BREAKER NR 152 POPPED AND SMOKED. TROUBLESHOT SYSTEM AND FOUND WIRING CHAFING IN OVERHEAD P5 PANEL GOING TO 'WHEEL WELL FIRE DETECTION MODULE'. REPAIRED WIRING AND MASTER DIM AND TEST SYSTEM OPERATION NORMAL. (M)