To find it, you'll likely need to:
1. Consult your owner's manual: This is the best starting point. The manual should have a diagram showing the fuse and relay box layout.
2. Look for a fuse and relay panel under the dash: It's typically located near the steering column or under the glove box. Access may require removing some trim panels.
3. Examine the relay panel closely: The relay may be labeled, or you might need to use a wiring diagram (obtainable online or from a repair manual) to identify it based on its connections. Many relays are interchangeable, so looking at the diagram will help to pinpoint the specific one for the blower motor.
If you can't find it easily, a local auto parts store employee might be able to assist. They usually have access to diagrams and can often guide you based on your truck's specific details.