To find it, you'll need to do some investigating:
1. Consult your owner's manual: This is the best place to start. The manual should have a wiring diagram and potentially a component location diagram.
2. Check fuse boxes and relay panels: These are usually located under the hood, often near the battery or under the dash. Look for a panel with multiple relays, some of which may be labeled. Some are even labeled with the glow plug symbol, which resembles a coil of wire.
3. Follow the glow plug wiring: Trace the wires leading from the glow plugs. They should lead back to the relay. This might require removing some components for better visibility.
4. Use a wiring diagram: A wiring diagram specific to your year and model truck is invaluable. You can often find these online through forums dedicated to International trucks or from a repair manual specific to your truck.
5. Online forums and communities: Search online forums dedicated to International trucks (like the International Harvester forums). Describe your truck's specifics (model, cab style, etc.) and ask for help. Someone with similar experience might have already solved this.
Important safety note: Always disconnect the negative battery terminal before working on any electrical components.
Because there's no single definitive answer, careful searching and potentially some investigative work within your vehicle's electrical system are necessary.
