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The FL is more than likely the pressure switch sticking closed. The head pressure may be keeping it closed for a while or the diaphragm is just getting old and stiff. Either way 4 years old get a new pressure switch.The circuit board did not cause the GFCI to trip. If all he did was change the board and the tripping stopped it was probably a connection issue.Service techs like this really get under my skin. This tech needs to go back to Burger King were he is qualified.Gary
I would simply as him to repalce the pressure switch, and try the old board. Pressure switches do go bad, some will leak internally, and on some cirucuits they can trip the GFI.A board is seldom the cause of a GFI problem.