The W124 and W126 CCU's don't have any sort of "overload protection" built into them. If the pump seizes (I've dealt with 3 of them now), they burn out a transistor on the board. Problem solved.

Since the OP was working in the cluster area, check the main plug on the key switch. There is a dedicated circuit off the main switch for the fan motor. It's possible the wiring got disturbed or disconnected somehow. Otherwise, it's likely coincidental.