2002 Passat 1.9TDI AVF - Radiator cooling fan always running

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Baker89

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Hi all,

I'm nearly at the end of my tether with this issue.

As soon as my engine is running, the radiator fan is running until the engine is switched off. This is regardless of whether the Climatronic AC is on or off.

So far, I have replaced, Coolant Temp Sensor, Fan Thermostatic switch (in the lower radiator hose), Thermostat.

I have removed all 370 & 373 relays one by one from the 2 relay rails behind the drivers knew roll and that makes no difference. According to my local VW dealer, my vehicle does not have a Fan Control Module as part of the system.

The weird thing is, the car does get up to the correct temp (90c) and sits there unless I'm sat still and have the heater on full blast on a high temp.

Does anyone have any suggestions? or do I just leave it be? I'm tearing out what little hair I have left 🤣

Thanks in advance.
 
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Bruce

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Have you pulled a wiring diagram and looked at the voltages on the pins at the fan motor connection? Is it possible that there is a wiring issue where the motor + lead is being shorted to +12?

I am assuming that the relay replacement eliminated a welded contact but there could be something going on in the socket for the relay. Have you checked?

I think to troubleshoot this, a meter and wiring diagram are in order.
 
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Baker89

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Have you pulled a wiring diagram and looked at the voltages on the pins at the fan motor connection? Is it possible that there is a wiring issue where the motor + lead is being shorted to +12?

I am assuming that the relay replacement eliminated a welded contact but there could be something going on in the socket for the relay. Have you checked?

I think to troubleshoot this, a meter and wiring diagram are in order.

I've not gone down that route yet. I'm working away at the minute, so thought I'd post on the forums for my next steps.

I haven't replaced the relays, I removed them 1 by one and none of them stopped the fan from running.

Once I get home, I'll get the multi-meter out and purchase a day of erWIN.

Would VCDS also help to pick up any issues, function tests?
 
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Bruce

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I haven't replaced the relays, I removed them 1 by one and none of them stopped the fan from running.
There is a huge clue... if the relay is out, how can the fan run? Presumably the fan is controlled by a relay. I don't think it was controlled by a module... but maybe...

So you haven't even tried pulling the fuse for the fan? I'm assuming that since you did not consult the wiring diagrams, you are not even sure which fuse should control the fan.

Yep, meter and wiring diagrams... that's what is needed here.
 
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Baker89

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There is a huge clue... if the relay is out, how can the fan run? Presumably the fan is controlled by a relay. I don't think it was controlled by a module... but maybe...

So you haven't even tried pulling the fuse for the fan? I'm assuming that since you did not consult the wiring diagrams, you are not even sure which fuse should control the fan.

Yep, meter and wiring diagrams... that's what is needed here.

I have a Haynes manual and according to that, there is no fuse for the radiator fan. The relays listed in the manual do not correspond to my layout of relays that I have.

I'll consult erWIN as I had no idea that existed until you linked it earlier.
 
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Dr Sheldon

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So far, I have replaced, Coolant Temp Sensor, Fan Thermostatic switch (in the lower radiator hose), Thermostat.

I have removed all 370 & 373 relays one by one from the 2 relay rails behind the drivers knew roll and that makes no difference.
Does anyone have any suggestions?
YES !! Stop replacing parts !!! Start Testing !!

Next can we see an AUTOSCAN Please.
 
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Dr Sheldon

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That car may have a single or two speed fan. Both Versions are fused and are controlled by a Relay(s).

A thermal Fan Switch exists.
 
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