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Temperature depending cooling fan in car

Discussion in 'Electronic Basics' started by ytreboe, Jan 4, 2004.

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  1. ytreboe

    ytreboe Guest

    I have an old car and I want to install an electric 12V cooling fan instead
    of the belt driven.

    I would like the fan to vary rpm depending on temperature. (higher temp=
    higher rpm.)
    Is this diffivult to make? New cars has this type.

    I have a 12 V fan from a n old japanese car. What do else I need to make it?

    Ps I'm not so much in the electronic business
  2. bj

    bj Guest

    I am not an expert in either electronics or mechanical engineering
    but the way I see your problem is this
    1) You do not need to vary the fan rpm depending on temperature--- all you
    need to do is switch the fan on when the engine is getting too hot----most
    of the time when you are just driving along there will be enough air flow
    through the radiator to keep the engine happy---and also running a bit more
    efficiently because this brainless fan is not running all the time.
    2) So now most of your problems are mechanical ones ---apart from getting a
    fused 12v feed to the fan
    a) Have you got enough room to mount the fan to the radiator? --bearing in
    mind that the fan belt was probably driving the water pump as well and you
    will have to keep this going all the time
    3) The switch that normally turns these fans on in modern cars---either
    because you are stuck in a traffic jam , or making the engine work hard ie.
    towing someting really heavy--- is usually located at the bottom of the
    radiator and you will have to get one of these and somehow plumb it into
    your own radiator--or probably the hose leading to it
    4)when you are testing all all of this remember that if the engine is
    overheating a little bit you can cool it down by turning the heating in the
    car onto max and fan on full and open the windows

    hope this helps

  3. DaveC

    DaveC Guest

    These electric fans typically mount forward of the radiator -- between it and
    the grille.
  4. ytreboe

    ytreboe Guest

    The problem is how to vary the speed of the fan. Not the mechanical. On my
    former car I built it in the traditional way. With thermostat on/off.
    The problem now is to make it like a new Mercedes. The hotter the engine
    is,the more rpm on the fan.
  5. the Wiz

    the Wiz Guest

    If you want more than on/off control, you're looking at much more sophisticated
    control system.

    The simplest system would be to have multiple thermostats, with the lowest
    temperature thermostat provided very reduced power to the fan (just enough
    voltage/current to move more air than the vehicle's speed). The next thermostat
    would provide more drive to the fan, and the highest temperature thermostat
    would provide full voltage to the fan.

    Better control will require some electronics. You'll need a microprocessor of
    some type to do the following:
    1. monitor actual coolant temperature
    2. control PWM motor controller to provide full control of fan speed

    Since you're building this from scratch, you might want to include a standard
    thermostat that switches full voltage to the fan if the electronics fail when
    the engine is hot ;-)

    More about me:
    VB3/VB6/C/PowerBasic source code:
    Freeware for the Palm with NS Basic source code:
    Drivers for Pablo graphics tablet and JamCam cameras:
    johnecarter [email protected] mindspring com. Fix the obvious to reply by email.
  6. If you want a Mercedes.....
  7. Guest

    It already exists
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