SteveR83

So have a small update on this for anyone interested. My local garage did squeeze me in to take a look but unfortunately didn't have time to actually replace the thermostat. They did agree that it's almost certainly in need of replacing and the cause of the coolant temp not getting to full temp. They also ran a scan and confirmed that the fan control module had error codes so the whole unit needed to be replaced. Think they said the genuine part was about £280 but also said if I wanted to buy non-genuine they would fit for me. Does anyone have experience of these cheaper radiator fan units? They any good, or just a false economy? Also, I am trying to find the exact part number for the fan unit, is there anywhere I can find that online? There seems to be a few variations of this part depending on year etc/engine etc.

I think I have come to the same conclusion Cliff regarding the thermostat, and I think Stevey is also probably right about the fan control unit. Changing the thermostat looks beyond my ability unfortunately, especially considering the lack of time I would have during a weekend in case anything went wrong! I will be taking it to my local garage next week who will change the thermostat and look at the fans at the same time - Hopefully there is a simple wiring issue with the fans but if it needs a whole new unit then so be it. Hopefully that will sort all my issues, as Stevey says the ECON issue is hopefully a byproduct of the faulty fans. Thanks for all the suggestions, will let you know how it goes!

Thanks, yeah I have already taken the bolted fuse off for the radiator fans and have driven a few times with them disconnected. Even without the fans on at all the temperature guage won't get above 70 degrees.

Thanks, that is what I was trying to understand. It didn't seem likely to me that the thermostat would cause the fans to come on. The temperature guage appears to be working normally, it drops to the lowest reading when the engine is cold and rises to about 70 within the first 10 minutes of driving and then stays there - It doesn't behave erratically or jump around. On the cheap bluetooth obd scanner, it shows the coolant temp at the same temp the dash says. I don't have an infra red meter unfortunately, but when I get a chance I was planning on running the car from cold and feeling the hose from the thermostat to the radiator to try and see if it slowly warms up which I believe would suggest the thermostat is stuck open?

Hi Jason, thanks I will have a look at the relays this evening.

Hi Gareth, and thanks. I think you're probably right, it makes sense to start with a new thermostat. I was hoping it would be the temp sensors as I could attempt to replace those myself. Do you happen to know if a dodgy thermostat could be causing both radiator fans to be constantly on? That is the main reason I am not quite sure..

Hoping someone might be able to shed a little light on an issue I am currently having with my 2008 A3 8P 1.9TDi. I noticed recently, in the last couple months, that I was getting noticeably worse mpg, and have now since realised that both the radiator fans come on immediately when starting the car, even from cold first thing in the morning. They stay on all the time when driving too. They even come on if I just turn the ignition on without actually starting the engine. They never stay on after removing the key though like I have seen others having issues with. The car is also not getting up to normal temp, it gets no further than about 70 degrees, but then pretty much stays at that temp. Also with the climate control system on, the ECON button is on and cannot be turned off. I have one of those cheapo bluetooth obd scanners which I have used to scan for errors with the Torque Pro app, but it doesnt find any problems. So, I have now removed the 50A bolted on fuse to stop the radiator fans coming on at all. I was thinking them being on might be why the car couldn't get up to 90 degrees, but even without the radiator fans on it is still getting no further than 70 degrees. The ECON button is also still on and cannot be turned off. I have read various threads about similar issues, but am unsure where this problem may be - The radiator fans themselves, the coolant temp sensor, or the thermostat. If the thermostat is faulty, could that cause both radiator fans to run at full speed immediately? If it was a coolant temp sensor, wouldn't I get an error code? Hopefully someone has had the same issue before!? Any help appreciated.