What was found
WING ANTI ICE L+ R ORANGE LIGHT WHEN WING ANTI ICE SELECTED ON, R ANTI ICE LIGHT WENT OUT AFTER APPROX 1 MIN. L WING ANTI ICE LIGHT STAYED ON FOR APPROX 4 MINS. EVENTUALLY CLEARED. GROUNDED - YES. PERFORMED LEFT WING THERMAL ANTI ICE VALVE HEALTH CHECK REF B737-9 AMM 30-11-11. OPS CHECK GOOD NO DEFECTS NOTED AT THIS TIME ON LH ANTI ICE VALVE. PERFORMED WING THERMAL ANTI ICE VALVE OPS TEST WITH APU BLEED PNEUMATIC AIR REF AMM 30-11-11. OPS CHECK GOOD NO DEFECTS NOTED AT THIS TIME ON RH ANTI ICE VALVE.