To find it, you'll likely need to:
1. Remove the glovebox: This usually involves unscrewing a few screws or clips. Consult your owner's manual for the precise procedure.
2. Look behind the glovebox: Once the glovebox is out, the resistor should be visible. It's often a small, rectangular black box with several wires connected to it.
If you can't find it behind the glovebox, it might be located in a slightly different place, perhaps near the blower motor itself under the dashboard. A wiring diagram specific to your van's year and model would be helpful in that case. You can often find these diagrams online through Ford parts websites or automotive repair manuals.