To find the correct fuse, you must consult your owner's manual. The manual will have a fuse diagram showing which fuse protects the wiper motor and its amperage rating. If you don't have the manual, you can often find a PDF version online through a Ford parts website or a search engine.
Looking at the fuse box itself, there will also usually be a diagram printed on the cover or inside the cover that shows the fuse layout and what each fuse protects. However, even this diagram may not explicitly state the amperage, only the location for the wiper motor fuse. You would then need to check the fuse itself to see the amperage rating printed on it.
Do not simply guess at the fuse amperage. Using a fuse with too low an amperage can cause the fuse to blow repeatedly, while using a fuse with too high an amperage can lead to a fire hazard.
