The location of the rear wiper fuse in a Ford Excursion varies slightly depending on the year.
You'll need to consult your owner's manual. The manual will have a diagram showing the fuse box layout and identify which fuse is for the rear wiper.
The fuse box is typically located either under the hood or inside the vehicle, often near the driver's side. Don't just rely on online forums; the owner's manual is your best and safest source of this information.