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Thread: Radiator fan wont turn off

  1. #1
    Junior Member ericdidit is on a distinguished road ericdidit's Avatar
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    Default Radiator fan wont turn off

    Any idea why this is happening?

    It was running for about 4 hours until my neighbor told me it was making sounds.

    I had to unplug it.

    Is it a broken thermostat?

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  3. #2
    Senior Member FER92VR6 is on a distinguished road FER92VR6's Avatar
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    Default Re: Radiator fan wont turn off

    check thermo switch (bottom of radiator on the driver side) maybe a bad temp sensor, or it could be a bad relay. if i was you id just run the fan to a switch in the car so you can turn it on and off when ever and you can have the fan on after you turn the car off.
    1992 Jetta. Nothing cool about it.

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    Not a VW fanboy 96JettaGLmk3 is on a distinguished road 96JettaGLmk3's Avatar
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    Default Re: Radiator fan wont turn off

    I agree, check the thermo switch on the radiator, easy fix.
    Follow my instagram @Mmattheeww

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    Junior Member ericdidit is on a distinguished road ericdidit's Avatar
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    Default Re: Radiator fan wont turn off

    you mean the Fan Switch?

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    Senior Member FER92VR6 is on a distinguished road FER92VR6's Avatar
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    Default Re: Radiator fan wont turn off

    its a sensor on the bottom of the radiator on the driver side. it looks like this or will look similar.


    http://www.techtonicstuning.com/main/images/121.116.jpg
    1992 Jetta. Nothing cool about it.

  7. #6
    Digifook. CafeRacer is on a distinguished road CafeRacer's Avatar
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    Default Re: Radiator fan wont turn off

    My first Mk2 had the same issue. Learnt alot about these cars with that old girl. Anyways. It can been one or both of 2 things. If the harness doesnt look stock, as alot of them have been repaird and poorly test it for cross grounding.

    If everything there looks alright there and the connections look good buy yourself a new thermo temp switch/sensor. Its located on the bottom drivers side of the rad. If your quick with the wrench you can lay a tray under the spill out and get away with only dumping half a beer can or so of coolant. You can buy them good ones cheap. If you live where its hot I sudggest buying a low temp fan switch. This will give you less panic moments watching the temp guage climbing and not hearing the fan kick in.

  8. #7
    Senior Member pieshi is on a distinguished road pieshi's Avatar
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    Default Re: Radiator fan wont turn off

    Whats the normal amount of time it shout run after a hot run?

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    Default Re: Radiator fan wont turn off

    That depends on a few things. If you just have the single speed fan, a 2 speed fan, if your car is equipped with the run on air temp sensor behind the valve cover and if it works correctly. A lot of the time they don't work after 15 years. Years worth of engine heat and oil like debris ruining the ground. Just another piece of German electronic engineering.

    If you pull up to a parking spot and the fan is on it will stay on for a few min at tops. If you have a 2 speed fan it should kick onto the high speed. More or less to prevent hot spots in the rad. If it turns on after you key off the car its because the run on air temp sensor is telling the car "Oi its hot in here and there isn't any air flow anymore flush this hot air out!"

  10. #9
    VERY Senior Member jcjetta is on a distinguished road jcjetta's Avatar
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    Default Re: Radiator fan wont turn off

    Anybody's electronics are prone to issues after 15 years!

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    Junior Member ericdidit is on a distinguished road ericdidit's Avatar
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    Default Re: Radiator fan wont turn off

    Thanks for all the help!

    I have not had a chance to check it out yet. Same thing is happening on my 1992 Cabbie,
    and its not the same engine layout as on my jetta.

    Also, the engine temp is running very high, but i have coolant!!

    Any other ideas?

  12. #11
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    Default Re: Radiator fan wont turn off

    A comfortable Mk2 temp is in about the middle of the guage on the dash. Obviously it goes down with air flow. If it creeps up then the fan should kick on. If you have a low temp thermo switch installed already or a bigger rad it may only get to half way before the fan kicks on.

    If its running hot I would check to see that the water system is circulating properly, warm it up and start feeling hoses too and from the rad and the pump. Most times the thermostat fails in the open position but I have seen a few fail closed witch can attribute to extra warmth. You may also be getting a false reading from a failing temp sender.

    I would change the thermo switch out for the low temp one and get a new temp sender while your at it too see if that changes anything. That will solve your fan issues right there. If it still continues to run hotter than normal you may want to take on cleaning the cooling system out.

  13. #12

    Default Re: Radiator fan wont turn off

    relay terminal oxidizes and turns green...clean it and replace the relay....

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