As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) FUEL FILTER WARNING LIGHT FLICKERS WHEN THE ENGINE IS AT IDLE. THE LIGHT FLICKERING INCREASES IN BRIGHTNESS WHEN THE CLUTCH IS DISENGAGED OR AUX FUEL PUMP IS TURNED OFF. THE SWITCH ASSY WAS REPLACED WITH REVISION D FOR TROUBLESHOOTING AND THE PROBLEM WAS RESOLVED. REVISION D IS SET TO 2.0 INCHES OF HG. REVISION F IS SET TO 2.75 INCHES OF HG.