What was found
NUMBER 1 ANTI-ICE TAI ILLUMINATED AMBER WITH SWITCH IN ON POSITION. POSITIONING SWITCH TO OFF TAI AMBER GOES AWAY. BLUE COWL VALVE OPEN LIGHT OPERATES NORMALLY. GROUNDED-YES. REMOVED AND REPLACED NR 1 ENGINE ANTI-ICE PRESSURE SENSOR. INSTALLATION TEST GOOD, REF B737-800 AMM 30-21-21. INSTALLATION TEST GOOD, REF AMM 30-21-21. ACCOMPLISHED NR 1 ENGINE COWL TAI VALVE OPERATIONS CHECK DURING ENGINE RUN. OPERATIONS CHECK GOOD, REF AMM 30-21-21. AMBER LIGHT FOR NR 1 ENGINE ANTI-ICE DID NOT ILLUMINATE WITH SWITCH IN ON POSITION.