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  • Low speed fan not working

    Hi all, before I start, apologies if I make myself look an idiot, still rather new to these vehicles. Trying to figure things out in a rush.

    The low speed on my cooling fan doesn't kick in , the only fans I have are at roughly 90 degrees plus 3 - 4 lines (roughly 1 line below the first dot). It sounds like a jet engine when these come on so reading other people's experiences I'm assuming this is the high speed.

    I've tried switching relays round but to no avail, I checked the fuse, I've bypassed what I've been told was the resistor (10mm nut onto the fan cowling, 2 wires either side), still no joy, the thermostat and everything else works as it Should, but this is causing the vehicle to run rather hot which I'm not happy with.

    I'm wondering if you lovely ladies and gentlemen would be able to lead me onto the right path before I burn it. I've attempted Google but I can't seem to find what I'm looking for (if someone can find a link I will love you forever)

    My questions are:
    Is this the correct resister I've bypassed or have I been an idiot?
    The sensor in the bottom of the rad, the wires have been messed around with in the past, what does this sensor control?
    I did read about some replacement MFTS sensors causing high temp issues, I don't know 100% the history of the vehicle, is there a way around this or just replace and hope?

    Love you lots

    EDIT: I'VE BEEN AN IDIOT FURTHER RESEARCH SHOWS ON 3B THE RESISTOR IS IN THE FAN, VERY SORRY.
    Last edited by z7999; 18 July 2017, 21:36.

  • #2
    Is this helpful at all?
    http://www.s2forum.com/forum/showthread.php?t=59802

    If the MFTS is not a original 4 pin one its likely to give a higher reading than the actual temperature. The most sane temperature reading would be from the sensor the ecu uses which you would need to interrogate the ecu with either VagCom or VCDS and then its in a numerical value which is not the actual temperature!

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    • #3
      That link is very helpful thank you sir. I think I was just being an idiot though. I was told there was no internal resistor in the fan however after reading a few posts it appears the 3b does but aby doesnt. Hence the confusion haha

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      • #4
        Its a bit confusing.
        Although there are 3 stages the fan only has 2 speeds. The 1st stage runs the fan first speed through the external resistor so its not a full speed. This is used for both the aircon and the after run I believe. The 2nd stage is run from the rad temp sensor at the bottom of the rad which is the normal everyday speed. The 3rd stage is the jet engine speed again from the sensor in the rad.
        The MFTS does not control the fan at all.
        Hope thats a bit clearer.

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        • #5
          Low speed fan not working

          So you have 3 wires down at the Otter Switch at the bottom of the rad.
          Try connecting two of these together in the 3 different combinations.
          One combination will give nothing.
          The other 2 combinations should give the 2 different speeds.
          If this is not the case you have a wiring fault or the resistor inside the fan motor is dead.

          If you do get the 2 speeds, medium and high, then replace the otter switch or correct the wiring to it.

          The MFTS feeds the gauge, a lot of aftermarket replacements make the gauge read falsely high.

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          • #6
            I see I see. If I replace the MFTS for an oe quality (if that's still possible?) Would that then allow the gauge to read normal again? I will check today if mine is 4 pin or 3 pin

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            • #7
              The problem is the 4 pin one has been obsolete for about 20 odd years. So unless one turns up as NOS somewhwere the only alternative would be a used one that still functions or a 3 pin one that is inaccurate. Even then they seem to have different readings between the various brands.
              I would take a look at the rad sensor if you think the wiring has been messed with. Perhaps one contact has died and has been bypassed. As I suggested earlier without knowing what temp the engine is at when the fans kick in and out its difficult to judge. If you can get someone to connect vagcom/Vcds and monitor the temp then that might put you mind at rest as to whether its running too hot/fan function.
              Last edited by twoqu; 19 July 2017, 13:03.

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