Hi, my name is Marty. There is no external fuse for the windshield washer pump on this model. The washer pump is fuse internally through the front signal acquisition module. The most common problem is a faulty washer pump itself. A voltage test needs to be performed at the washer pump connector to verify that there is voltage present when the washer switch is depressed. If you have voltage to the connector the washer pump will need to be replaced.
Please let me know if you have any questions.
Hi, the washer pump is located in the side of the windshield washer container. I am assuming your car is a C class Mercedes.
Let me know if you need anything else.