The heater blower resistor on a Ford F-250 is typically located
behind the glove box. However, the exact location can vary slightly depending on the year and model of your F-250. You might need to remove the glove box entirely to access it. It's usually a small, rectangular unit with several wires connected.
Before attempting to access it, consult your owner's manual or a repair manual specific to your vehicle's year and model. This will provide the most accurate location and removal instructions. Pictures or diagrams are invaluable in this process.