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Thread: Electric Fans

  1. #1

    Default Electric Fans

    Just a question, what's the deal with electric fans? I've read alot about them on this site, but no clue how they work in comparison to the stock fan thats in my truck right now. I know someone(s) out there who can do some explaining to me, and if their worth the investment.

  2. #2
    Jr. Engineer jwco5.3's Avatar
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    Mechanical fan is a big fan that runs off a clutch on your motor... the motor actually drives it. So there is a parasitic loss from the energy it takes to drive the fan, costing you horsepower and gas mileage.

    Electric fans run off the battery, so there is no parasitic loss. I have heard of gains of .5 to 1.5 mpg by switching to electric fans, although I have not done so yet and cannot vouch for any number. I have heard of a noticable difference in power as well, which is believable since you will not be turning a large fan with engine power.

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    X2 what Jwco said. One of the biggest gains comes from the electric fans not running ALL the time, whereas your mechanical fan IS always turning & robbing hp & mpg. While there is a small parasitic loss with the electrics due to the alternator having to put back into the battery, what the electric fans have taken out, it is a miniscule amount compared to the mechanical fan running all the time. Once you are up to about 30 mph & above, there is enough air passing through your radiator to keep your engine cool, & your electrics will very seldom come on except maybe if you are towing a heavy load uphill on a hot day. As far as actual mpg gain, for my kind of driving & a 5,000 lb. truck, I netted an extra .6 -.7 mpg with 2 - 14" electrics. One is on a thermostat & the other I put on a manual switch, & it's seldom necessary to use it except when towing in the summer with temps over 80 degrees. I also switch the fans (wiring) every 2 years to keep the hours equal on them.
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  4. #4
    Jr. Engineer jwco5.3's Avatar
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    Thanks Stephan. I did not think of only running one fan on the thermostat. How exactly did you wire everything?

  5. #5
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    I wired the fans separately JW. I bought one (1) adjustable thermostat. I have it wired into one of the fans (through the ign. switch so it doesn't run after the engine has been shut off) & the other fan I wired through a manual switch to battery + so I only turn it on when pulling a hill in hot weather when towing if engine temp approaches 200 degrees F. The thermostat is a very simple two wire stat with a capillary tube that is adjustable via a rheostat so you can adjust it to come on sooner in the summer, & at a delayed temp in winter when you very seldom need it. Both fans are 2 wire linear induction motors (very thin) so there are no issues with clearance btw the engine & radiator. Rather than hardwiring them in, I put quick disconnects on the wires so I can easily switch them to keep the hours equal.

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