Electric Fan Conversions and AMPs

Electric fans are not all bad.  They are just a misunderstood technology.  I get asked all the time about stuff like the Taurus e-fan mod (or Lincoln Mark) for cooling different engines.

Lets start by saying yes electric fans can cool a vehicle when properly used.  That last part is key.  Not all fans are alike and most people do not get it.  You cannot just slap a pair of 12″ universal electric fans from you local parts store and expect them to cool your truck the same as the fan clutch that was on there.  Period.  No exceptions.  Shrouding is the first reason (see my older post about why shrouding is important – wont waste our time with more of that here) and the fan motor/wiring is the second reason.

OE manufacturers spend hundreds of thousands (millions over the years) in R&D to ensure proper cooling can be achieved with an electric fan.  What makes you think you can short cut this with 2x 12″ fans off the shelf?   OE manufacturers also go a step further and use heavy duty 4 pole motors with adequate wiring from high amperage relays and fuses.  More recently they have moved into using Pulse Width Modification (essentially the PCM supplies a ground to the system as the switch).  This allows for less amp spikes on the power side of things allowing for smaller wires and cheaper components to save a couple of bucks per car.  These universal fans and controllers at the parts stores are great for adding cooling, but should not be used as a primary source of cooling unless you know what you are doing.  If you see terms in this article you do not know or have to look them up then you likely DO NOT KNOW WHAT YOU ARE DOING.  Universal fans also have another draw back – they are a 2 pole design.  While economical and compact they are not designed for continuous use.  Most of the universal fans on the market are 2 pole.  Believe me; if someone manufactures a 4 pole fan they will market the crap out of it as being so… those that understand electric fans will recognize this advantage and jump all over it.  Powering the fan motors is another issue.

All fan motors have whats known as Locked Rotor Current (LRC).  As fan motors are energized a large amount of amperage is required to build an electrical field through the windings to get the motor turning.  Often times this amperage draw (although temporary) is much higher than the fuses/relays.  I have measured some amp draws as high as 90 amps for the OE 4 pole motors (similar to the Taurus fan).  There is no universal controller on the market (as I am writing this at the end of 2015) that will handle 90+ amps.  You’ll have to build you own setup with solenoids, relays, etc, to get the reliability you want.  Once a motor is moving the current required to push the motor along is minimal – this is where the amperage drops off.  Interestingly enough – look at fan ratings for current draw.  The ones that are lower are generally a more efficient motor or use better quality parts.  Cheap motors require large amounts of amps to do the same work – little tid bit to save you some $$$ down the road.


So after all that research, custom wiring, additional parts past just the fan and controller… how many miles will you have to drive around saving 2 mpg when a fan clutch is usually under $50?

P. Heffcac

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