Electric cooling fan & amps

Discussion in 'Electrical Systems' started by larrylarry, Nov 27, 2012.

  1. larrylarry

    larrylarry Veteran Member

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    Dec 22, 2011
    San Antonio Tx
    When I was playing around with my cooling fan,I had it connected to my battery charger to make sure it worked,I notice it would spin faster as I increased the amps. How can I increase the amps to the fan. I'm guessing that they only pull as much as they need. Is their a way I can bump it up some like 10 or 15 amps more. It is a 2 wire fan.
     
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  2. Gary S

    Gary S Administrator Lifetime Gold Member

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    Most electric fans require a lot of amperage to run properly. You will most likely need to put on a larger alternator to handle it.
     
  3. flak monkey

    flak monkey Veteran Member Lifetime Gold Member

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    Norfolk, UK
    As long as you maintain the voltage it will pull what it needs amps wise. If it needs 150W at full load to maintain its speed then it will draw current dependant on volts (P=IV).

    Wire it with something like 14g wire through a relay and it will be fine. Normally they pull approx 10-15a running, inductive load on start up might be up to 75% more.

    If the wires too small and a long run you'll get excessive voltage drop which will affect its performance. Good 16ga thinwall cable will carry 16a happily, but needs de-rating for long lengths.

    Voltage can also drop if your alternator can't keep up with demand. But just adding an electric fan, assuming the rest of the electrical system is good shouldn't cause a problem for the stock 63a alternator. If youve got a massive stereo, fuel injection and a load of extras then it might be an issue!
     
    Last edited: Nov 27, 2012
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  4. larrylarry

    larrylarry Veteran Member

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    Dec 22, 2011
    San Antonio Tx
    I have a 100w alternator, an I used 10 GA. to supply voltage from the starter.One thing I forgot to add was Im using an adjustable temp.sw. from a smaller cooling fan an it has its own relay wired to the adjustable temp. sw. I don't know if the temp. sw. limits the amps. or not. I also used 10 ga. wire from the temp. sw. to the fan. If I could get the fan to run 15 or 20% faster it would help on hot days.
     
  5. flak monkey

    flak monkey Veteran Member Lifetime Gold Member

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    Aug 5, 2011
    Norfolk, UK
    Measure the voltage at the fan terminals, and at the alternator with the motor running. If they are the same, then you have no voltage drop and you wont be able to make the fan spin any faster.

    If you have any more than 0.5volt drop then you have a problem somewhere.
     
  6. CDesperado

    CDesperado Veteran Member Lifetime Gold Member

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    Dallas Texas
    What is the CFM rating on the fans you are using?
     
  7. larrylarry

    larrylarry Veteran Member

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    Dec 22, 2011
    San Antonio Tx
    I don't know what the cmf is, I got it off a Lincoln continental, it 17" wide. It was almost to big for my radiator. Infact about 1/2 in. of the fan hangs down at the bottom of the Rad. I did get the shroud to fit around it.
     
  8. mjoc

    mjoc Veteran Member

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    Apr 29, 2003
    Sherman Oaks, Ca

    If you are installing an electric fan you should run relays. and run large gauge wire to and from relays. also you a large amp relay like a 40amp. It will allow the fan to pull move amperage if needed..

    Michael
     
  9. larrylarry

    larrylarry Veteran Member

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    Dec 22, 2011
    San Antonio Tx
    Thanks for the info.
     
  10. z28_Baby

    z28_Baby New Member

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    Jan 19, 2017
    Flak, what is the advantage of thinwall in terms of voltage drop?
    I haven't been using thinwall cable before now.
     

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