I got a call on a PLC in a control panel I built for controlling hydraulic ram pumps used in locking bridge cranes together.
User: "Your control system is not engaging the rams, the pump mfr told me to call you because you programmed that PLC."
Me: "Is the hydraulic pump running?"
User: "Yes, but the rams are not extending. You need to get down here right away."
Me: "There is nothing in the PLC that would prevent the rams from extending if the pump is running. There is no valve control or anything like that, the pump ONLY goes to the ram."
User: "I didn't want an excuse, I want you down here NOW."
Me: "Give me an open PO, I charge $150/hr for field work, portal to portal, you are 3 hours away. If it's my fault, no charge. If it is something else, full charge. Agreed?"
User: "Yes, dammit, just get down here!"
3 hours and 30 seconds later, I look at the sight glass on the hydraulic pump, there is no oil in it. The big red tag ON THE PUMP that says 'WARNING! DO NOT OPERATE WITHOUT FILLING OIL RESERVOIR!" is still in place on the fill cap.