As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING DEPARTURE CLIMB UPON GEAR RETRACTION, LANDING GEAR HANDLE COULD NOT BE RAISED BEYOND OFF POSITION. NO LEFT MAIN GEAR DOOR INDICATION ON SECOND OFFICER'S ANNUNCIATION PANEL. AURAL WARNING HORN WAS SOUNDING UPON FLAP RETRACITON WITH GEAR DOWN. FLIGHT RETURNED TO DTW WITHOUT FURTHER INCIDENT. MAINTENANCE INSTALLED A SERVICEABLE LANDING GEAR ACCESSORY UNIT. OPERATIONAL CHECK NORMAL.