What was found
DURING FLIGHT 2968, LT INTAKE HEAT CYCLES. LT INTAKE LIGHT ILLUMINATES W/MASTER CAUTION THEN EXTINGUISHES AFTER 5-15 SECONDS. AIR RETURN TO DTW. MAINTENANCE T/S SYSTEM. FOUND CHIPS IN LOWER INTAKE DUCT HEATER MAT. ALL CHECKS GOOD. REMOVED AND REPLACED LT LOWER INLET DUCT ASSEMBLY P/N NH24668-169, SN/ON L169264, SN/OFF L291137. ALL CHECKS GOOD IAW CHAP 30 SF340 MM.