What was found
NO EQUIP COOLING LIGHT ILLUMINATED AT FL180 ON CLIMB-OUT. QRH COMPLIED WITH EQUIP COOLING CIRCUIT BREAKERS PULLED FOR 15 SECONDS & RESET. LIGHT WENT OUT & REMAINED OUT FOR ABOUT 2 MINS THEN RE-ILLUMINATED. CB PULL IAW QRH. LIGHT EXTINGUISHED DURING APPROACH. REMOVED EQUIPMENT COOLING SYSTEM FLOW STRAIGHTNER AND MUFFLER. FOUND INSIDE INSULATION LOOSE & BLOCKING AIR EXIT. R & R FLOW STRAIGHTNER & MUFFLER IAW MM 21-58-061-4. PER MTSI WRI 21-26/1509. R & R FLOW CONTROL VALVE IAW MM 21-58-021-4. GROUND PRESSURIZED ACFT IAW JRH, WHEN FLOW CONTROL VALVE CLOSED EQUIP COOLING LIGHT REMAINED OFF. EQUIP COOLING SYS GROUND OP'S CKD GOOD PER MM 21-58-021-4, 21-58-061-4, 21-58-000-0. ACFT OK FOR SERVICE.