90 Accord fan relay/motor

I'm having what seems to be a not-so-uncommon problem in my 90 Accord,
where it overheats if not moving enough. After having cooling work
done, with the accompanying pressure test coming out ok (and most of
the system now replaced in the past year and a half), I checked the
cooling fan fuse. Blown. Replaced it, turned on the car, that fuse blew
immediately. What's the likely culprit? How much should the fix cost me?

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