What was found
EMERGENCY LIGHTS IN CABIN COME ON WHEN ENG ANTI ICE IS TURNED ON. IT HAPPENED EVERY TIME THE ANTI -ICE SWITCHES WERE CYCLED IN FLIGHT. PERFORMED EMERGENCY LIGHTING TEST IAW TSM 33-52-00-810-881A . TEST PASSED. PERFORMED OPS CHECK OF ENG ICE PROTECTION SYSTEM WITH ENGINES RUNNING. IAW AMM 30-21. TESTS PASSED, BOTH ENGINES. COULD NOT DUPLICATE FAULT. NO 30 DAY HISTORY NOTED. ACFT OK FOR SVC. (LP: 8934568, AIRCRAFT WAS GROUNDED)