I was called-in by a local customer to find an intermittent nuisance trouble. It’s hard to see in this picture but this little glass fast acting fuse was causing some interesting machine trouble. The fuse failed with a thin fracture in the filament which would open and close intermittently through a heating/cooling effect and vibration. While troubleshooting this 110 ton Engel injection molding machine I noticed that all PLC outputs would loose power, dropping out all hydraulic valve solenoid power. I managed to be measuring the 24vdc power supply when the problem occured and knew it was fine. Examining the schematic I noticed the fuse was in the dc supply line feeding the PLC2 output common.