If you can't find it in either place, you could try:
* Checking online forums: Search online forums dedicated to Ford E-350 motorhomes or RV repair. Someone might have had the same question and posted the answer.
* Contacting a Ford dealership or RV repair shop: They might have access to wiring diagrams for your specific model.
Important Note: Before working with any electrical components, disconnect the negative battery terminal to avoid electrical shock or damage.