What was found
AFTER TAKEOFF AT PHX EN ROUTE FOR MSP RECEIVED EICAS MESSAGE -L ENG ANTI-ICE- WITH NR 1 ENGINE ANTI-ICE VALVE LIGHT ILLUMINATED. DUE TO ICING CONDITIONS AT MSP TURNED BACK TO PHX FOR REPAIR. MAINTENANCE REMOVED AND REPLACED NR 1 ENGINE ANTI-ICE VALVE, DID NOT CORRECT THE PROBLEM, REPLACED ENGINE ANTI-ICE LOW PRESSURE SWITCH IAW BMM 30-21-01. PERFORMED ENGINE RUN, ANTI-ICE VALVE OPERATED NORMALLY, NO LIGHT OR EICAS MESSAGES NOTED. FUNCTIONAL TEST OF ANTI-ICE LOW PRESSURE SWITCH S/N TR565 WAS NO FAULT FOUND, INSULATION, LEAKAGE, AND CALIBRATION TESTS WERE GOOD.