As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THAT DURING FLIGHT THE AC ESS BUS CAUTION MESSAGE ILLUMINATED IN FLIGHT. TROUBLESHOOTING DETERMINED THE CENTRAL BUS RELAY P/N HA4A039 AND VOLTAGE SENSOR RELAY B0804074-001 TO BE DEFECTIVE. INSTALLED NEW RELAYS. FUNCTIONAL CHECKS SATISFACTORY.