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Thread: Force Rad Fan to Run

  1. #1
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    Question Force Rad Fan to Run

    Is there a way to force the fan to run as a diagnostic test?

    I don't have working A/C as the condenser has been holed

    Thanks
    Paul
    Pure 2000 W, LHD 599cc - Engine Rebuilt Feb 08 - sold
    Passion 2000 W, LHD 599cc - Engine Rebuilt Mar 09 - sold
    Passion 1998 T, LHD 599cc - Engine Rebuilt Apr 10 - sold
    Cabrio 2001 Y, LHD 599cc - Engine Rebuilt Jul 10 Replaced Oct 16

  2. #2
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    If it's only the fan being checked, hot wire directly from battery - or cig lighter socket.

  3. #3
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    I think you can tell it to run in Xentry and maybe Delphi if you can find the right setting.

  4. #4
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    It's just that I can't ever remember hearing the fan run, only the intercooler fan

    So I'm just as interested in the controller as the fan itself

    The car does reach 4 blobs when in traffic, but I've never seen it go higher

    With some cars you can force the fans to run by switching on the A/C, or disconnecting the coolant temp sender
    Paul
    Pure 2000 W, LHD 599cc - Engine Rebuilt Feb 08 - sold
    Passion 2000 W, LHD 599cc - Engine Rebuilt Mar 09 - sold
    Passion 1998 T, LHD 599cc - Engine Rebuilt Apr 10 - sold
    Cabrio 2001 Y, LHD 599cc - Engine Rebuilt Jul 10 Replaced Oct 16

  5. #5
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    Radiator cooling fan can be tested using a variable resistor wired in to connector for engine coolant temperature sensor.

    Estimate your variable resistor based on below details:

    , where

    B = Beta value = 3988 Kelvin, R0 = 3000 Ohm at reference temperature T0 (298K or +25C).
    R is measured resistance of thermistor at temperature T (in Kelvin).
    Drives a Smart Cdi - 65 to 85 MPG

  6. #6
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    Quote Originally Posted by Mjolinor View Post
    I think you can tell it to run in Xentry and maybe Delphi if you can find the right setting.
    Sadly I don't have access to either
    Paul
    Pure 2000 W, LHD 599cc - Engine Rebuilt Feb 08 - sold
    Passion 2000 W, LHD 599cc - Engine Rebuilt Mar 09 - sold
    Passion 1998 T, LHD 599cc - Engine Rebuilt Apr 10 - sold
    Cabrio 2001 Y, LHD 599cc - Engine Rebuilt Jul 10 Replaced Oct 16

  7. #7
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    Quote Originally Posted by UKKid35 View Post
    It's just that I can't ever remember hearing the fan run, only the intercooler fan
    They very rarely run.....

    Quote Originally Posted by UKKid35 View Post
    The car does reach 4 blobs when in traffic, but I've never seen it go higher
    .....even when (just about as rarely) 4 blobs show. Which on my car has been twice during fast idle MOT emissions tests and once in snow so deep it was throwing the snow chains off.

  8. #8
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    Quote Originally Posted by tolsen View Post
    Radiator cooling fan can be tested using a variable resistor wired in to connector for engine coolant temperature sensor.
    Thanks, since I'm not looking to test whether it cuts in at the right temp, it sounds like it should run if I either disconnect the sensor, or short it (not quite sure which)



    Quote Originally Posted by pinger View Post
    They very rarely run.....

    .....even when (just about as rarely) 4 blobs show. Which on my car has been twice during fast idle MOT emissions tests and once in snow so deep it was throwing the snow chains off.
    So I'm probably concerned about nothing anyway...
    Paul
    Pure 2000 W, LHD 599cc - Engine Rebuilt Feb 08 - sold
    Passion 2000 W, LHD 599cc - Engine Rebuilt Mar 09 - sold
    Passion 1998 T, LHD 599cc - Engine Rebuilt Apr 10 - sold
    Cabrio 2001 Y, LHD 599cc - Engine Rebuilt Jul 10 Replaced Oct 16

  9. #9
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    Both my 450 and 451 have never run the fan in seven years or so except when I did it deliberately.

  10. #10
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    Open circuit to air inlet sensor makes intercooler fan run constantly so probably same for radiator fan as more serious if engine overheats.
    Drives a Smart Cdi - 65 to 85 MPG

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