Many years ago I converted to an electric fan. The first try was a kit with a 10 inch fan and a bulb controller that went into the rad. The fan wasn't big enough and the metal line to the bulb broke. End of that.
  The next fan and support was from a Citation, and the controller was a rad hose sensor from a Holley water injection kit. I ran it from the battery without a relay or fuse, and it did a pretty good job until one plug broke off the sensor. I ground down the potting plastic and resoldered it, and epoxied it over, and it worked again. This time I used a relay and wired it into the ignition.
  Still, overall the fan gave out vibrations and was ugly, and as horsepower grew I changed over to the plastic viscous fan.
  Now I wanted to try an electric fan again. This time I checked over the possibilities first and knew a little more about electrical stuff.
  The first thing was the controller. I wanted something off the shelf of the local auto parts store. A selection of temps. would be nice, and some way to hook it to the rad. system. There were kits out there but I felt they were ugly and unreliable. Some mail order places sell a temp sensor that screwed into a 3/8 port, but they charged $50.00 or more. Factory sensors turned on only at high temps.

 This is what I found. It was standard on most European cars in the 1980's and it comes in a variety of temps. The 2 shown turn on/off at 85/80 and 92/87 celsius.

 The bad thing is that they are a large metric 22 x 1.5 mm thread. I got around this by taking the fitting out of the original rad.

 The only difference between the 2 brands is the socket size. Most will take a 1 1/8 while a few needs a 30mm. You need to bend in the ears to get the socket on, or a special socket. Then crack it loose, and work the ratchet back and forth to break the fitting out of the rad. I took my fittings from burnt out BMWs. I've later found that a Saab Turbo has a tube in the upper rad hose that takes this sensor.
 Several used ones were tested and they all opened at the correct temperatures so they are reliable.
 I soldered the fitting into my rad by the cap. It was the only flat area on the tanks. For the High speed fan I used a sensor from a 4 cylinder mustang, which threads into the thermostat housing. A housing from a van has the proper threads if yours is blanked off.
 A standard spade plug will fit on the ears. In the photo Audi plugs are shown, but I used Volvo AC plugs with a 90 degree bend.

Some of the following pictures are from other sites. If there's no record on the photo, I have no idea from where it came. I include them here to have all the choices in one place. They are all factory units, because they are the best. They are made to work and avoid warranty problems.

	The Lincoln Mark VIII fan. The big daddy of the Do It Yourselfer. It can be bought new or used and is fairly cheap.The earlier years were more powerful while later models were altered to make them more quiet. It can still suck twice as much air as a common fan. It sucks a lot of amps too so make sure your alternator is up to it. Here is a wiring site.
The fan from the Taurus 3.8 L. At 16in it is bigger and more powerful than the common 3.0 type. It has a pancake motor while the smaller one has a can type. It is also a bit of an amp hog.  They are becoming more common as the Tauruses get older.  The same fan blade and motor is on the SN 95 Mustangs and newer Volvos too.
	These are Windstar dual fans. Notice that one motor is flat and the other a can. I guess there's an advantage to two. If one goes bad there is still some cooling. http://www.geocities.com/diels12000/WindstarFans.html
98 Camaro dual fans. They look kind of small to me, but they cool a powerful engine. They had a unique way of functioning, using 3 relays for high and low speed. At low speed both fans grounded through one relay, effectively giving each fan half the volts. At high speed each had its' own ground, giving full voltage.
	Some Crown Victorias from the 1990s had an electric fan inside the fan shroud. Even though the main fan was engine driven, heavy duty cooling cars had an electric as a backup in case of overheating. I don't know the CFM but with 18 inch blades they must move some air. I tested it in the house, laying it flat on the floor and it sucked all the crap out of the carpet. In cops cars they kept idling engines cool all day. In civilian cars they were only backup so were hardly used and are in good shape. Look for the 2 wire plug entering the shroud on top of the passenger side. They are bolted to the shroud with 3 tabs.
I found two good fans in Oldsmobiles. There are many 14 inch GM fans but fewer 16 inch. Here is the only 16 inch with curved blades that I ever saw. It is a 2 speed with the resistor wiring attached and uses the can type motor. It seems powerful but I don't know the specs. The resistor is 65ohm 50W. My plan when I bought it was to cut off the tabs and mount it inside the stock Ford shroud. I saw this on someone elses' site and they said it worked quite well. I haven't got around to installing it yet. The wiring connector is poor and I've found newer type wiring, and relays all in one.
	This is a 7 blade 16 inch from an Olds with a V8 Diesel mounted sideways. I didn't know there was such a thing.  The fan has a metal frame and a pancake motor. It has 2 speeds; High, and Typhoon! When I hooked it up to the charger I thought high was running, until the other wire was attached. Papers blew across the garage, dust swirled, and the side door slammed shut!  Olds has the best GM fans, or had, now that they're extinct.
The fans that were marketed by Ramchargers. Some say these are Dodge fans from a newer Intrepid.
	Contour dual fans pull 3400 CFM in total, so they say. The fan is also over an inch thinner than the Taurus fan at the motors, and it is a little less then 3 inches thick between the motors where the water pump pulley will be, so it is a much easier fit between the water pump pulley and the radiator.