As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF ORD-DTW, THE FORWARD ACCESSORY COMPARTMENT DOOR WARNING LIGHT ILLUMINATED. RETURNED TO ORD WITHOUT FURTHER INCIDENT. THE WARNING LIGHT EXTINGUISHED ON LANDING AND REMAINED OUT DURING TAXI. CLEANED DOOR SWITCH CONNECTION AND RELAMPED ANNUNCIATOR AS PRECAUTIONARY. INDICATION AND DOOR LATCHING MECHANISM CHECKED OK.