As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 2997 - DURING FLIGHT, LEFT OIL COOLER DUCT HEAT WOULD NOT OPERATE. PULLED AND RESET CIRCUIT BREAKER WITH NO CHANGE. FLIGHT RETURNED TO DTW. MAINTENANCE INSPECTED OIL COOLER DUCT HEAT AND CANNON PLUG. NO DEFECTS NOTED. MAINTENANCE PERFORMED FUNCTIONAL CHECK IAW SA-227 MM 30-20-10. ALL CHECKS GOOD. (M)