As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT NR 3319 RT INTAKE HEAT FAILED. RT INTAKE HEAT ANNUNCIATOR ILLUMINATED REPEATILY WHILE INFLIGHT. CYCLED ON AND OFF EVERY 20 SECONDS. QRH COMPLETED. NO ABNORMAL ENGINE INDICATIONS WERE NOTED. AIR RETURN TO DTW DUE TO WEATHER. MAINTENANCE REMOVED AND REPLACED ENGINE UPPER DUCT ASSEMBLY IAW TASKCARD 7160-302. OPS CHECK OF RT INTAKE HEAT SYSTEM IAW MM IS GOOD.