Sorry it's a bit late but still may be of use. From memory, the coolers on these machines have a pressure switch and a small pcb that send a signal back to the machine when the water is flowing. Pressure switches clog after a while and generally cannot be fixed. You could try shorting the two wires on the switch and that should stop the warning light. However, if the pump isn't turning, then this will not help. Check the pump rotates first!
Dave