To find it, you'll need to:
1. Consult your owner's manual: This is the best place to start. The manual should have a fuse and relay diagram.
2. Check the fuse box under the hood: Many Ford vehicles of that era placed relays in the under-hood fuse box. Look for a diagram on the inside of the fuse box cover. The relay may be labeled, or you might need to trace wires to identify it.
3. Check the fuse box inside the vehicle: Some relays, particularly for less critical circuits, were located in the interior fuse panel (often under the dashboard).
4. Look for a separate relay center: Some higher-end or option-heavy vehicles had a separate relay center, often near the battery or in the engine compartment.
Because there's no single definitive location, you'll need to do some detective work using the above steps. If you cannot locate it using your owner's manual and visual inspection, consult a Ford repair manual specific to your vehicle's year and model or seek help from a mechanic.