On Ford products the fan resistor is almost always mounted in the plenum right after the fan/blower. All that's visible is a multi-wire connector and a couple screws that hold it in place.
I used to drive Ford company vehicles and for some reason their fan resistors are a frequent replacement item. On my personal vehicles (non-Ford) I don't recall ever having to replace one.
"A wise man can change his mind. A fool never will."
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2018 Flagstaff Micro Lite 25BDS
2004 Nissan Titan