Production is shut down! Oil has leaked everywhere. Management is screaming to get the line going again. You hit the GO button and nothing moves. You’ve done some troubleshooting; you’ve got power, you’ve got a functional hydraulic system. Everything is working except for one function. all these signs tell you that a hydraulic valve is the culprit. You race to the stock room and grab a replacement. It bolts up to the same place, works on the same voltage, plugs back in without any new wiring, and it seems everything is resolved.