2005 1.6 FSI - Cooling Fans and Temperature Sensor Problem

[Peter OJ]

Morning All,
I need a bit of help and advice for my son.He has a 2005 Mk 5 Golf, 1.6 FSI and has been having problems with both fans running at maximum from cold and the amber exhaust system warning light is on.
The fault first appeared at the end of September, he took the car to the garage (VW dealer) and they changed a Temperature Sensor (VHCV1070).All was OK for just over two weeks and the fault reappeared.The garage changed the sensor again under parts warranty.Again, all was OK for just over three weeks when, yet again, the fault reappeared.Once again they changed the sensor under parts warranty.But once more, after just over two weeks, the fault has reappeared.
Symptoms are as follows:

• First indication is that the amber exhaust system warning light comes on.
  
  
• When the car is stopped, both fans are running at max.
  
  
• From a cold start, Ignition On, engine not running and with Econ On and A/C Off, both fans are off. When the engine is started, after 5 seconds both fans start to run at normal speed. By 18 seconds both fans are running at maximum speed.
  
• Switching the A/C On or Econ Off has no effect, the symptoms are the same.
  Clearly, something is causing the temperature sensor to blow, because once it’s changed the car is OK for a while.
  Has anyone had similar problems or have any idea what could be causing this problem?
  Thanks for any help you can give.
  PJ
  

[Rookie84]

Hi Peter, this sounds very similar to a problem I had on a 1.6FSi, 2004. The problem was caused by a second coolant temperature sensor (on engine, not the one at bottom of radiator), which was signalling that the engine was overheating. The first garage I visited (a VW dealer!) couldn't diagnose it but kept suggesting the sensor at the radiator outlet. This was also causing my car to stall as it was under-fuelling to reduce engine temperature. I am not sure if maybe the under/over fuelling could be related to your enginer temp and hence causing emission problems, and therefore your exhaust system warning light to come on.

[valentinbirsan]

Hello Peter OJ,

I had the same car, but it is from 2004 (1.6FSI) and the same problem, I think. After the engine start the both cooling fans are turn of after a randomly time, even if the engine is cold. I scanned the car with VCDS and have no error (DTC) set. Both fans are new.
If you are kind please tell me how do you handled this issue.

Thanks in advance!

[Crasher]

Hello Peter, is this the blue one we have in today?