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Cooling fans always run


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Hi guys not been on here for ages hope everyone is well :).

 

I've had my MK2 Jetta VR6 2.8 12V OBD2 AAA for about 18months on the road and I've got to say I love it. Apart from a coil pack melt down and now this bug bear its been faultless too which is nice :).

 

just after some proper technical help my cooling fans are running all the time, I've done a code read and faulted G65 sensor which I replaced (blue 2 pin coolant temp) I know this is used for engine management not the cooling fans so no big surprise the fans still run.

 

I've tested my fan switch in the rad and that's okay, when I take the 20amp fuse from my fan ECU all is well and the fans works through the switch instead, although this prevents my AUX water pump running with I'm not that chuffed about.

 

I deduce that the fan ECU os being told to switch on the fans via something what I don't know ??? Does anyone know what signalls the ecu to run the fans ?

 

The engine was from a Highline so it had AC but its all taken off now. I've plugged in a new brown 4 pin sensor and still the same :/. Any help would be very helpful

 

On another note the fans turn off with the AUX on after run if this helps

 

Thanks in advance sorry for the long post :)

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Hi guys thanks for the reply. I'm not sure what speed it is running at I assume 3 because its being triggered by the control unit. I've had a look at the control unit and it doesn't look corroded etc.

 

I'll have a play tomorrow and see what speed it is running at. I thought that the yellow sensor is for the dash panel and the brown is for the fan ?

 

Does anyone know how to test the fan ECU I assume its a 4 pin relay in essence but not sure about the smaller plug. Does anyone know what voltage etc I should have at the two plugs or have a current flow diagram as I don't have one.

 

Thanks Rob

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I've checked my fan speed and I seems to be running at speed one. None of my wiring seems to be corroded / damage. it is controlled by the 20 amp fuse in my radiator control unit but I'm unsure of what controls that circuit.

 

I've also in plugged all the sensors in the thermos stat housing to no avail =[

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