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Thread: Front cooling fan

  1. #21
    Join Date
    Nov 2007
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    BANCHORY
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    3,128
    Source a 1k potentiometer. Connect in place of temperature sensor. Fan should cut in at about 187 Ohm or about 103 C.
    Drives a Smart Cdi - 65 to 85 MPG

  2. #22
    Join Date
    Mar 2010
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    Hampshire
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    Optimal temperature for the suprex is 88deg - though it will deviate from this during normal use.
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  3. #23
    Join Date
    Apr 2009
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    Ecosse
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    3,478
    Quote Originally Posted by Heinkeljb View Post
    Question: At what temperature is the front fan supposed to come on?
    If this helps....
    On my (2005) car I've only known the fan come on twice - and each time it alerted me to the only times the temp gauge ever showed 4 blobs.

    Once while making very slow progress through snow so deep it was flinging the snow chains off, and the other during a tricky MOT emissions test where it was hanging with a load of rpm for the fast idle test with a failing cat.

  4. #24
    Join Date
    Feb 2011
    Location
    Lewes
    Posts
    698
    The biggest problem with the Temperature gauge in the 450 is that one "blob" covers 20 degrees celsius! Using Star diagnostics allows me to see real time temperature in 1 degree accuracy.

    Come the weekend when I have daylight again, I will put some dye in the header tank and then try to get the temperature up to between 100 and 120 degrees - hopefully we won't get to 120 degrees before the fan comes on, but considering the fact that last week it did get high enough for the display to start blinking and beeping without the fan coming on. I think there is some other fault which needs sorting, but other than knowing it is down to some bit of electronics in the ZEE, I am at a loss as to how to fix that issue.

    John

  5. #25
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    Nov 2007
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    You will struggle getting your engine hot enough this time of the year. Better to test fan operation by wiring in a potentiometer. Perhaps also check temperature sensor by immersing in boiling water.
    Drives a Smart Cdi - 65 to 85 MPG

  6. #26
    Join Date
    Feb 2011
    Location
    Lewes
    Posts
    698
    Star reports the temperature from the temperature sensor in 1 degree increments, it goes up along with the "blobs" and the change from one blob to two blobs happens at 59 / 60 degrees as expected, the same when it gets to 79 / 80 degrees. The same when it gets to 99 / 100 degrees. So I don't think there is anything wrong with the sensor.
    Star can turn the fan on and off, so nothing wrong with the fan.
    Just seems to be something wrong with the trigger point when it should turn on the fan, because it doesn't.

    As it appears to be behaving itself at the moment staying at 3 Blobs and Star reported 89 / 90 degrees on my commute to work and back, I shall wait till the weekend before doing anything, because it is easier to work in daylight than by touch light.

    John

  7. #27
    Join Date
    Mar 2012
    Location
    Burnley
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    1,242
    My 451 fan has some dubious habits. When starting from cold it comes on about 20 metres into the drive and goes off at about 40 metres. It will do that randomly throughout any journey when I set off from 0 mph.

    This is long before I even have one blob on the temperature gauge but I don't mind it doing that because it lets me know it is working.

  8. #28
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    Nov 2007
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    Since radiator fan cuts in above 100C, you need a fully sealed leak free cooling system to reach that temperature. If there is a leak somewhere or expansion cap is not sealing, then the pressure in the coolant system will just vent/ boil off and coolant won't get hot enough for fan to cut in.
    Drives a Smart Cdi - 65 to 85 MPG

  9. #29
    Join Date
    Nov 2007
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    BANCHORY
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    Tested fan operation just now on my 2002 Smart 450 with potentiometer. Fan cuts in at 100C and out when temperature drops below 95C.
    Drives a Smart Cdi - 65 to 85 MPG

  10. #30
    Join Date
    Feb 2011
    Location
    Lewes
    Posts
    698
    As I have managed to get the temperature up above 100C with star diagnostics attached and the fan did not turn on, I presume there is a difference between petrol and diesel versions software, or i have a fault in the Zee.
    Maybe I should disconnect the battery for a while as it has not been disconnected for 3 + years at least. Is there any computer electronics in the Zee that would / could benefit from that sort of reset?

    How did you connect the potentiometer, just stuffed the wires into the connector instead of the sensor? Did you let the engine warm up to normal operating temperature before you connected the potentiometer and then turn it to the 187 Ohms you mention in an earlier post? I am just trying to get things straight before I attempted more tests at the weekend.

    John

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