HI, I WAS HAVING ISSUES WITH ST CODE EVEN WITH CUTTING AIR(WATER) BUT, ONLY WITH COND. C900'S WHICH IS A PICA CIRCUT USED FOR FINAL PASS. THE TECH FIXED MY ISSUES BY CHANGING 5S BOX THAT IS LOCATED OUTSIDE AND BEHINHD THE WORK TANK. MY MACHINE IS ABOUT 20 YEARS OLD. SOME HOW DIRT BUILT UP IN THIS BOX AND OVER HEATED CAUSING WIRES TO MELT.