A windscreen washer pump is a small pump that feeds fluid from the windscreen wash reservoir to the washer nozzles. The pump is powered by a motor, which is needed to generate enough pressure to force the liquid along the washer feed tubes and out of the washer nozzles on the windscreen, headlights or rear window.
The washer pump is attached to the base of the screenwash reservoir. On some cars, there may be two pumps and two motors, serving both the front and rear windscreens. Often, the easiest way to access the windscreen washer pump is from underneath the car, but on some models, you may need to remove one of the front wheels and access it through the open wheel arch.
If you aren’t sure where your windscreen washer pump is, follow the washer nozzle feed lines from the top of the firewall (the place where the engine bay meets the passenger compartment). Alternatively, your manual should provide a diagram of the engine layout.