My Gn has only 11000 miles and probably all original brake parts. The pressure switch is the upgraded gray not black. The car ran and stopped fine( for a buick anyway!) then the brake light flashed on for less than a second each time the pedal was depressed relatively hard. I had a shop look at it and they said it was fine and a momentary flash is OK. I returning from the track one night and lost all power assist and the brake light came on and stayed on. I nursed it home and got out my GM diagnostic manuals and first thing was to check the 30Amp fuse. It was blown. I replaced the accumulator anyway and replaced the fuse but after the booster pressurizes the system the brake light will go out and all is well until I put the pedal all the way to the floor. It will blow the fuse. I have tried four fuses and blew them all so there must be an underlying problem that is way beyond my limited powermaster knowledge. Help