As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLOW CHECK, FOUND PROPORTIONING VALVE MALFUNTIONING. INTERNAL CHECK VALVE INOP LETTING FLUID IN LINES TO PANELS BLEED BACK INTO TANK. IAW OPS CHECK, THE CHECK CAN BE DONE THREE TIMES. THE VALVE FAILED EACH TIME. REPLACED VALVE WITH ANOTHER NEW VALVE WHICH THEN PASSED THE FLOW CHECK.