What was found
PHL - FLT 14 - AFTER TAKEOFF FROM PHL, THE LEFT ENGINE BLEED LIGHT ILLUMINATED WITH SELECTION OF ENGINE ANTI-ICE. THE DUCT PRESSURE DECREASED TO FIVE PSI. THE PRESSURE RETURNED TO NORMAL WITH THE ANTI-ICE OFF. DUE TO DESTINATION WEATHER CONDITIONS, THE FLIGHT RETURNED TO PHL AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE COULD NOT DUPLICATE THE CONDITION ON THE GROUND. THE LEFT ENGINE BLEED CARD WAS REPLACED AS A PRECAUTION. VERIFICATION FLIGHT WAS FLOWN WITH NO FURTHER PROBLEMS. (M)