A FAULTY SENSOR CAN CAUSE OVERHEATING

I READ your response to Charlotte regarding the problem she experienced with her Golf. I have the same problem with my Golf 4 (2 000 model) and when I took it for a service I was told that the problem might be the "control unit", which, unfortunately costs over R11 000, VAT included.

I READ your response to Charlotte regarding the problem she experienced with her Golf. I have the same problem with my Golf 4 (2 000 model) and when I took it for a service I was told that the problem might be the "control unit", which, unfortunately costs over R11 000, VAT included.

I think I will have to check on this 4-pin water temperature sensor to see what difference it will make. Possibly the same unit has also affected my aircon as it is now not functioning.

Another problem I have noticed is overheating when traffic is congestedand I have to drive very slowly. Is there any link between these problems? D K Pilane

IN VIEW of the fact that one of the functions of the suspect water temperature sensor is to control the switching on and off of the electrically-operated radiator fan, there is a possibility that a faulty sensor could cause the fan to come on later than it should (or not at all) when the temperature rises.

During open-road driving the fan is seldom needed, the natural airflow through the radiator core of the moving car being sufficient to carry away the heat released by the circulating coolant.

But in slow-moving traffic and prolonged stop/start conditions there is insufficient natural airflow, and you need the fan to force air through the radiator core.

When a car with an electric fan overheats only in slow-moving traffic, the working of the fan is therefore the first thing to check.

In your case, where the sensor controlling the fan is already suspect, the overheating just strengthens the suspicions.

The coolant temperature sensor on the Golf 4 engine is found on the side facing the air filter housing, where the top radiator hose is connected to the cylinder head.

The price of the sensor, including the new O-ring, as shown on the picture, was given by VW agents at R302, VAT included.

Ideally one would like to test the output signal of the sensor first to see whether it is indeed faulty, before replacing it, but that will cost you more money.

In this case the indications are so strong that I would opt to have the sensor replaced without further ado if I were in your shoes.

There could be a connection between a faulty sensor and the fact that the aircon is inoperative, but it could also be an entirely unrelated problem.

If the aircon does not come to life after you have replaced the sensor, I suggest you take the car to an automotive aircon specialist. (I would just check the aircon's fuse in the fuse box before I take the car in!)

As far as the diagnosis of "faulty ECU" is concerned, I don't know what grounds the workshop had for this opinion but, at a price of R11 000, replacing the ECU would be the very last resort in my book.

There is a company in Joburg (Auto ECU, tel 011-615-6665/6/7, speak to Rob or Steven) which can repair a faulty ECU in certain cases. I believe the problems are due to "dry" solder joints which they can re-solder.

One has to give the motor manufacturers credit for making the basic components inside these "black boxes" very extremely reliable.

If the worst comes to the worst, and you really are looking at a faulty ECU, try to get it repaired first.

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