Engine Coolant Temperature Sensor 2.4 V6

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Hi I have a problem with my temperature gauge in that the needle never moves - it always shows a cold engine even with a decent run. Sometimes when the engine idles it drops revs and then quickly recovers them. Also the engine sounds a bit rough - just not as smooth as usual.

From reading other threads it sounds like this might be the culprit - either that or a stuck thermostat?

I called the dealer who quoted £37 for the ECT sensor which seems reasonable. I'd like to order it but I don't know where on this engine the sensor is located.

I have an A4 B5 2.4 V6.

A couple of days later the blowers for my climate control stopped working - Not sure if this fault is connected. I can hear it make a noise when i change the direction of the blowers but not the blowers themselves.

Any ideas greatly appreciated.

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Just an update - I stumbled accross the climate control diagnostic tool. When I went to option 51 (engine coolant temperature) the temperature showed as 80 - the car had only been running 2 or 3 minutes but i could see it increasing in real time. Does this mean that the sensor is working and I have a faulty needle?

[Randomhedgehog]

Hi, if you use option 49 on the climate diagnostics this will provide a more accurate coolant temperature which may help diagnosis.

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Hi, if you use option 49 on the climate diagnostics this will provide a more accurate coolant temperature which may help diagnosis.

I don't have the car right now but on the list I have 49 shows as malfunction counter for speedometer signal.

[Randomhedgehog]

Yep, says that on my list too but I found a reference to it being coolant temp elsewhere and my own tests showed this to be the case. I had a stuck open thermostat and was only reaching about 70c after a run and with the reading displayed could see the temp dropping on the motorway due to excess cooling. Replaced stat and now gauge reads to 90 as expected and this is confirmed by climate control readings.

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Thanks for replying. I do remember a few weeks ago on a trip to London from Scotland the temperature gauge dropped considerably on the motorway, I just assumed it was the colder weather coming in.
Did you experience any other symptoms with the faulty thermostat?
Is it hard to change?
Does the climate control diagnostics pull it's data from the engine coolant temp sensor? If so this would indicate my sensor is working properly, wouldn't it?

Sorry for all the questions.

[Randomhedgehog]

I didn't have any other symptoms beyond water and oil temperatures not getting up to expected levels though I would expect an increase in fuel consumption due to ecu thinking engine is cold and this may cause other symptoms as you have experienced.

Mine is a 1.8t so not sure about thermostat location or ease of change on yours but it was a simple fix for me though access was from underneath only.

The temp dropping on a motorway run would be a good indication that stat is stuck open. Also I believe that the climate panel temperature is taken direct from the sensor so it would seem it is working though as I said before I understand the reading on channel 49 is more accurate.

Hope this helps.

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My blowers randomly came back on this morning about 2 mins after i started driving and about 3 mins after i started the car so I immediately put the heating on and the air was really hot - does this still sound typical of a thermostat stuck open? I thought if it was stuck open then the engine would have a really hard time heating up let alone the water.

Cheers

[Randomhedgehog]

Would imagine that if the air is hot rather than warm then thermostat is not stuck open so problem is more likely to be the coolant temperature sensor, though it may just be the route that the water takes through the cooling system in that if it goes from engine to heat exchanger then onto radiator warm air could still be available. Have you had the opportunity to monitor the readings displayed on c49 of the climate control diagnostic mode yet, this will show if the sensor is providing a reading to the dash or not and what that reading is.

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I had the channel 49 up whilst I was driving today and the display rose steadily until it hit 49 degrees c and then dropped a little to 47. At the same time the oil gauge was showing 80 degrees c before i stopped. (It was a short trip)

The air was hot again. I'm starting to lean towards the sensor. To be honest I'm rather glad, I found out that on my car the timing belt has to be removed to get access to the thermostat. Having said that I cannot find any how to instructions to replace the sensor for the 2.4 v6, found 1.8T how to and 2.8 but none for my type. Is it true that the 2.8 is almost identical to mine?