Electric fans WILL require upgrade to 3G (130 amp) alternator. Many threads on what should be done with wiring. For me, I used a cable from a Windstar/Freestar that goes from alternator post right to battery positive. Simply clip off Freestar battery clamp and install a ring connector and attach to battery side of starter solenoid. Nice heavy gauge, its the right length and dirt cheap at wreckers. Some other wire changes for the connector into alt, but not too serious.
The biggest thing (and most debated) is how you control the fans. Some choose aftermarket controllers, some (like myself) went OEM parts and relay control (like the factory did), others simple toggle switch and a good temp gauge to make sure you get an accurate temp of the system. Whatever control system you go with I suggest that the temp probe (for aftermarket controllers), temp switch (for relay control) or temp gauge probe (for toggles) be in the lower rad hose. Why... Having temperature reading after the rad lets the rad do its thing. When it can't keep up on its own the fans need to come on. The only place to take the temp reading and accomplish this is in the discharge side of the rad (drive side rad tank or lower rad hose). Any point in the engine (likely intake or heater hoses) or upper rad hose is a reading of engine temperature, not coolant temperature. The thermostat controls engine temp, not the rad.
Sorry, I will get off my soap box now. I just find it difficult to read threads where owners are being pointed in the direction of systems that cost hundreds to thousands of dollars (price a 4 core aluminum rad, aftermarket dual electric fans, aftermarket fan controller). I am about to put 2010 F150 electric fans into my DD 2004 F150 Supercrew 4x4 and I am going to use the wiring and control system from a Contour as the basis. I got my fan for $35. Relay panel and wiring from a Contour 4-cyl (another former DD) - free, but would only be $10-20 at most pull-a-parts. Same dual speed fan switch and pigtail from a VW - $3 I think. I am going to add the thermo resistor from a Contour Fan to make F150 dual speed and control it same as I did my Mustang. The only challenge for the enthusiast who doesn't fabricate their own parts is the mount for the fan switch in the lower rad hose. Easiest way I can come up with is get a spindle nut from a Contour (M22x1.5 thread - same thread as the fan switch) and weld it to a piece of 1.5" pipe. Cut about 1-1.5" of lower rad hose, insert pipe, clamp and seal everything and now switch is in place. The rest is some basic wiring. So for potentially $50-60 you have a fan system that operates the way the factory designed it (although in a different car). I have had 3 Contour DD's with a total of over 700,000 km (about 450,000 miles) and not one failure of the relay based fan control system.
There will be haters of everything out there, I'm a K.I.S.S. guy. And why mess with a design that is not broken.
Again, sorry for the rant and potentially derailing the thread. If anyone wants more details, there is a thread here on this site where I detailed my Mustang system. I can always provide more details if desired. Enjoy your evening.
