What was found
CLIMBING OUT FLIGHT LEVEL 230 IN MCT STILL. IN ICING CONDITIONS ALL ANTI-ICE ON. AT APPROXIMATELY THREE MINUTES THE A/I ENGINE COLD L ILLUMINATED, AND DID NOT EXTINGUISH. WE INITIATED THE QRH AND ACCOMPLISH IT. THE LIGHT REMAIN ILLUMINATED THEN EXTINGUISH WITH THE L ENG BLD AIR HP SELECTED. WE EXIT ICING CONDITIONS AND PROCEED TO DESTINATION. NEXT FLIGHT WAS TO KLAS AND IT WAS IFR WITH RAIN. CORRECTIVE ACTION: REMOVED AND REPLACED #1 ENGINE INLET COWL ANT- ICE PRESSURE REGULATING SHUTOFF VALVE WITH CUSTOMER SUPPLIED UNIT IN ACCORDANCE WITH CESSNA 6B0A AMM 30-20-05. OPS AND LEAK CHECKS GOOD. INSTALLED VALVE INSPECTED BY C&L AVIATION SERVICES LLC, CERT# J2SR196J, WO# X1124, 24/DEC/2025