Okay, a quick fix for now would be to wire in a toggle switch and just kick it on whenever the engine is running. Simple, cheap, but effective.
For the permanent fix, you're going to have to order a new fan controller or do some microsurgery to get it reconnected. If you use solder, get stuff with a rosin core (NEVER ACID!!!) made for fine electrical work and a fine tipped soldering iron. If the controller box is plastic you can probably use the soldering iron to melt away enough of the casing to get to the connection. Hope this helps. Good luck!
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Capri306, Moderator, The Mustang Works Online
1979 Mercury Capri, 5.0L -- C4 -- 2.73
1987 Mustang LX Notch