What was found
EMERGENCY DECLARED, EQUIPMENT COOLING WAS INOP IN NORMAL AND ALTERNATE BUT STARTED TO WORK NORMAL ON DESCENT. UAL MX C/W BMM CHECK, NO FAULTS. A/C RETURNED TO PHX WITH SAME PROBLEM. MX FOUND SENSOR LOOSE IN DUCT. INFORMATION OBTAINED FROM MX CONTROL LOG SHEET, ADDITIONAL INFO TO FOLLOW.