As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER ENGINE START LEFT ENGINE ANTI ICE SWITCH TURNED ON AND COWL VALVE OPEN ANNUNCIATOR ILLUMINATED BRIGHT BLUE BUT DID NOT TURN DIM. CYCLED SWITCH ONCE AND THE SAME SCENARIO OCCURRED AGAIN. GROUNDED - YES. REMOVED AND REPLACED ENGINE 1 COWL TAI VALVE IAW B737-800 AMM 30-21-11-400-801. OPS CHECK GOOD ON GROUND IAW AMM SUB TASK 30-21-11-860-009.