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Another gti fan issue


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Hi all,

the fan on my gti isn’t coming on, I can’t say I recall it ever coming on previously but it isn’t now and after plugging into a obd sensor it got up to 105 and didn’t kick in.

ive bridged the switch connector and the fan comes on however keeps blowing the 20amp fuse in the engine bay.

im leaning on it being the fan switch, however....... I’ve found the fan relay under the passenger wing, is not connected at all, no signs of any plugs or connectors, the terminals are all corroded and look like they have never had any plugs on them.

 

any one with experience with this able to clear this up?

 

cheers

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50 minutes ago, mk2 said:

That'll be the fan motor. The bearings go then excessive friction causes high currents to flow and then pop goes the fuse...

Cheers for the response, so fan and the switch is bad then?

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  • 2 weeks later...

Just an update on this is anyone else has the same problem.

Seems there was 2 issues:

the fan only works at its high speed, assuming the resistor is goosed.

The switch isn't telling it to go onto its highspeed, the low speed might be working on the switch but there is no lowspeed on the fan to operate.

If anyone needs to replace a fan switch I recommend buying a 29mm DEEP socket, makes the job so much easier and quicker

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I would do away with the fan controller altogether - why do VW always seem to locate both this and ABS under the expansion tank plus pretty close to the exhaust?

For your rally application - the key thing is reliability - I would make up a new loom for fused relays to be mounted in a less destructive location within the cabin, but still using the thermostatic switch to activate the fan. 

Something that will give your coolant system a lot easier ride is an oil cooler.

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9 hours ago, LR5V said:

I would do away with the fan controller altogether - why do VW always seem to locate both this and ABS under the expansion tank plus pretty close to the exhaust?

For your rally application - the key thing is reliability - I would make up a new loom for fused relays to be mounted in a less destructive location within the cabin, but still using the thermostatic switch to activate the fan. 

Something that will give your coolant system a lot easier ride is an oil cooler.

When you say fan controller what do you mean? as far as im aware the fan is just controlled by the thermoswitch ? im going to wire up a switch to run in the cabin just incase it fails again i can flick it on.

i have thought about an oil cooler but am yet to have a problem with the factory cooling system so will see, they do make a massive difference on my 350z which love to cook its oil.

 

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The fan is powered with a PWM signal I think, although many vdubs just have a fan resistor inside the controller or fan. It means that the fan speed can varied from slow to fast. If you have AC, then the controller is linked to the ECU and AC to also adjust the engine RPM to compensate for extra compressor loading at idle. It isn't a basic switch... :) Only the much older vdubs have switches.

 

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I think the resistor in the fan is blown as i can only get high speed :(

Anyone able to shed light on why the fan relay box thing, under the passenger wing, is present on my car (no AC) but not connected?

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Sounds like someone before you has been messing up things... good luck! :)

so at least you have the controller, but not the loom that connects it to the fan and ecu. Time for some detective work me thinks. Let us know how you get on and how you fixed it.

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Fan controller looks like this, should be on a bracket under the expansion sphere:

image.jpeg.6561d0b2839589b65412d4c5e4787424.jpeg

If yours is different  or not there post a picture of your mystery relay? - the under the wing location sounds odd, or aftermarket for horns or lights

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that's the puppy,

It looked like it was in an OEM mounting and everything. Lights, horns etc all oem nothing looked messed with.

Really weird as the terminals were sooo corroded it looked like there had never been anything in them.

I thought maybe it used to have AC but there are no signs of any tampering.

very odd

 

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Yeah that's a standard vdub fan controller... they are fixable if they go wrong, but you need to be careful when you pull them to bits as the pins are molded into the wiring inside. Expensive to replace too. Should be connected to fan else fan will never ever run. The main switching relay that supplies power to the fan is inside this thing. Very curious to know what happened...

just had a thought- follow the wiring from the fan back. Should end up at this unit.

Edited by mk2
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the fan now works with the new thermoswitch,

there is no connectors near this modules, the module is in my front room now and the fan comes on so god knows. if I have any more problems ill dig a little deeper

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I made my guess what happened to it in my original post - the control module probably got soaked and baked in the awful location VW put it. 

Considering its just a couple of relays, it takes up a shed load of space.

Does your Gti have a sunroof? - no sunroof usually means AC fitted - you can check what options your Lupo came with on the white option sticker in the boot...but suspect it is gone after cage install, if you have the service book it should be in there as well, think if you ask very nicely at VW dealer they will dig out the info for you.

 

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