As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE, THE AIR TEMP SELECTOR WHILE IN AUTO MODE WAS MOVED TO A MORE COOL POSITION, WITH NO EFFECT. ECS SWITCH WAS MOVED TO MANUAL MODE AND MORE COOL WAS TOGGLE WITH THE MANUAL SWITCH. AIR TEMP STILL NOT GETTING COOLER. MINUTES LATER THE ECS CAUTION AMBER ADVISORY LIGHT LIT AND FLIGHT WAS RESUMED TO HOME BASE AS PER FLIGHT MANUAL. THIS PROCEDURE WAS TRIED A FEW TIMES WHILE EN ROUTE WITH THE SAME RESULT.