As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CREW PREFLIGHT, ODOR OF UNKNOWN ORIGIN WAS NOTED ON FLIGHT DECK WITH EXTERNAL POWER APPLIED. MAINTENANCE IDENTIFIED THE SOURCE OF ODOR TO BE AN EXTERNAL POWER CIRCUIT RESISTOR FOR THE INDICATION LIGHT. THE EXTERNAL POWER SYSTEM WAS DEFERRED IAW MEL 24-16, AND THE AIRCRAFT RETURNED TO SERVICE. S/D - REPLACED RESISTOR R4-19 IAW DACO M/M CHAPTER 20 AND CLEARED THE DEFERRED ITEM.