As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN FLIGHT WITH WING ANTI SWITCH OFF, THE L VALVE OPEN LIGHT IS ILLUMINATED BRIGHT BLUE. ACFT GROUNDED. OPS CHECKED THE WING ANTI ICE GOOD. COULD NOT DUPLICATE FAULT. VALVES OPERATE AND CYCLE NORMALLY. NO AIRCRAFT HISTORY. CONCLUDED THE DISCREPANCY IS AN INTERMITTENT FAULT.