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Electric Fan
Almost all of the new automobiles manufactured these days use electric fans instead of mechanical fans. The last year that the Ford Mustang utilized a mechanical fan was in 1993 when the motor was cooled with a heavy blade fan and clutch fan which was bolted directly to the water pump pulley that was spun off the crankshaft. So why is the mechanical fan less efficient than an electric fan? Since the mechanical fan speed is a function of crankshaft speed (or RPM), your fan will be spinning the slowest at low RPM, often times when you need airflow the most, at idle. The faster the fan spins, the greater the power loss at your rear wheels. Thus the mechanical fan hurts gas mileage and robs horsepower.
The battery in your car stores energy and converts chemical energy to electric energy. The beauty of an electric fan is that it utilizes the battery's stored energy to operate, and then the alternator charges the battery back up while you are driving. Although the load on the alternator is increased, the increase is intermittent and because of the weight of the fan, it doesn't compare to the load exhibited on your water pump pulley due to the mechanical fan. When paralleled with a controller and temperature sensor that turns the fan on above a set coolant temperature, an electric fan can be made to be very efficient. Also keep in mind that when the fan is on, it is at constant high speed and is not a function of RPM. So if your electric fan has a single speed setting, it will spin at the same speed at idle as it does at 5,000RPM, assuming you are using a temperature sensor and are operating above a threshold temperature.
I remember walking around a Pick-N-Pull wrecking yard one day when I stumbled upon a '92 3.8L Mercury sable. I noticed that it had an electric fan that looked to be in good condition with all the wiring in place which got me thinking. I know I remembered reading that any 3.8L Taurus/Sable fan is good to over 2000cfm on the high speed setting which is adequate for a lightly modified V8 302. I went ahead and pulled it off paying just $27 for it. The fan comes with three wires. Two are positive and correspond to high and low speed, and the third wire is ground. I took the fan home, tied away the low wire since I had no desire to run the fan at low speed, and brushed the two remaining leads across the leads of my car's 12V battery. Much to my delight the fan spun up quickly and was pushing a great deal of air.
I knew I was going to need a fan controller but wasn't sure which to get. In the past I used a Imperial/Hayden #226204 controller that I picked up at Kragan for about $40. It is about as cheap a controller as you could possibly buy. It uses a radiator feed-thru which is not very reliable or consistent. One major problem I had with it is that no matter how hot my motor was, as soon as I began to move forward causing air to run past the radiator probe, thus cooling it, the fan would instantly shut off. I knew that my next controller was going to have to be more reliable and eliminate this problem. The controller is shown below:
It is adjustable from 160-230 degrees F and is set to turn off 10 degrees F lower than the temperature that you have it set to turn on at.
It can be seen here on page 91
http://www.haydenauto.com/assets/2003%20ImperialCat.pdf
After doing some online research, I stumbled upon a few posts by "Blown88gt" from corral.net that indicated that Volkswagen actually had an oem switch that matched the on/off operating range perfectly for use with a 180* thermostat. The switch has a 198F on and a 189F off operating temp. It is an oem part that is made by Wahler in Germany, so you can have confidence that it is a quality part.
Remember, you always want the thermal switch to have a higher range than the stat, or the fan will never shut off. This switch could be threaded straight into the thermostat housing, and it only needs two wires for a clean looking install, unlike the Hayden/Imperial controller. The problem is that the switch requires a very rare metric M22-1.5 tap which I was able to locate after contacting about a dozen machine shops. Mcmaster.com also sells the tap, but it carries a $50 price tag. Before you tap, make sure to drill the housing with a 3/4" drill bit to make tapping more manageable.
This VW switch was standard equipment on the older (late 70's/early 80's) VW Rabbits, so it could be picked up from your local VW dealer. I'd like to thank "Blown88gt" for recommending the switch to me.
In addition, it is always a good idea to use a relay with any electric fan. When the fan is activated initially, there exists a current spike in excess of 100Amps for a very short period of time (on the order of microseconds), and this is the reason why there should be a relay used that is rated at an amperage close to the spike. Since the fan controller came with only a 30amp relay, I cut it away from the controller and purchased a Bosch 75amp relay #0332002156 from http://www.bpg-inc.com/
To mount the fan, you could use radiator feed-thru zip ties. It is also a Imperial/Hayden part #226201. Since I had a new radiator I was very apprehensive about using these types of ties, but I can assure you that they are very thin and hardly alter the radiator fins in any way.
It is also a good idea to use a reverse current blocking diode (or freewheeling diode) on any motor control relay. This prevents any reverse current from running thru the fan since the current will take the path of least resistance which in this case happens to be thru the diode. Once power is removed from a DC motor it becomes a DC generator and the reverse voltage spike can shorten the life of the relay. The 1N5408 diode can be found at Radio Shack.
Parts List and Prices
Part
Part#
Price
Taurus/Sable 3.8L Fan
$27
VW switch and gasket
823959481F
$50
Imperial/Hayden Mount Kit
226201
$10
Bosch 75Amp Relay
0-332002156
$32
freewheeling diode
1N5408
$1
Total
$120
Mounting the Fan:
Begin by removing your serpentine belt along with your stock fan and fan clutch as one unit (The fan is bolted to the water pump pulley via 4 bolts). Next unbolt the stock radiator fan shroud and remove it. Disconnect the radiator overflow from the stock shroud since you will reuse it. The Taurus/Sable 3.8L fan is not a direct bolt on and poses a problem with mounting the radiator overflow. I found a method to keep the overflow in the stock location without introducing any new coolant lines. Before you actually mount your fan to the radiator, it is a good idea to first mount the overflow to the fan shroud. I had to drill one large hole in the fan shroud for the middle overflow hole and use a 1 inch standoff to give it some structural rigidity. I used a large nut and bolt and compressed the overflow to the shroud via the standoff.
Then I drilled a small hole in the bottom inner mounting tab, and used that hole to make aligned marks on the bottom portion of the shroud where I was to drill the shroud. I used one long bolt and nut that would run thru the tab, via narrow standoffs, and shroud and compress the two together to further increase the structural integrity of the fan/overflow combo.
In order for the fan shroud to slide into the two metal lower radiator mounting tabs, the bottom bolt that was used to compress the overflow tab to the new shroud, had to have the bolt head grinded down very flat using a belt sander. The thickness of the bolt head is visible in the pics above. Once the overflow was completely bolted to the shroud, I simply slid the shroud into place.
Then I unbolted the two top radiator mounts that secure the radiator to the body and pushed the top of the radiator towards the rear of the car. This allowed me to secure the fan to the radiator using the radiator feed thru ties. I used three upper radiator feed thru ties to secure everything. Make sure to tie them tight to prevent the assembly from moving around on you while driving. The final step is to bolt the radiator back to the body and attach the overflow hose to the overflow.
The Controller Switch:
Here is the schematic:
Impressions: The 198/189F VW switch is a match made in heaven with the 180F thermostat. On the stock gauge I haven't seen any major changes compared to the mechanical fan. It runs cool as ever, only now it is doing so more efficiently. What is cool (no pun intended) is now you can actually hear more of the motor instead of having it drowned out by the loud mechanical fan. Seats of the pants shows an improvement as well...
*Note: Do not attempt to use an electric fan with the stock 87-93 alternator. It simply is not rated at high enough amperage to support charging the battery at the same rate that it is being discharged due to the fan. For reference I am using a 130amp 94-95GT alternator.
If you have any questions, please email me at: info@mustangmotorsport.com
