Trouble engine fan and temp indicator.

[sinenarockandroll]

Hi everyone

Just bought a Polo gti 9n3 a couple of months ago and I is already showing some problems.

Engine fan will keep turning for more than 1 hour after switching off the engine. To the point that I’ve already run flat of battery. And also the engine temperature indicator will not work properly – when engine is hot it will properly indicate 90º, but the suddenly the needle will drop to 45º. And if I turn off and instantly restart the engine the needle will go back to 90º.

The mechanic did not manage to solve the problem so he took the car to someone else that is used to work on electrical parts of the car.
He says the problem comes from the Climatronic ECU and has to be replaced. He is giving me a budget of 650 pounds for a new ECU + 300 pound for the installation.

Sounds crazy to me – is there no cheaper option?

[RUM4MO]

I would think that for the cost of an engine coolant temperature sensor, it would be worth replacing that to sort out the temperature being displayed changing like that, and if it does not, not much money wasted.

Fan running on for too long, you will need to try some things yourself if you can, and the first thing might be to unplug the cooling fan thermal switch to see if that stops the running fan, also before doing that, switch the AC to eco so that the AC compressor is not being asked to run.

The engine cooling fan, if only one fan is fitted to that car, should be a 2 speed fan, if the engine is cold and you switch on the AC system so that the compressor is being asked to chill the air, then the fan should get switched on to help the AC system dump heat. There is a cooling fan control module and that controls when the fan(s) run and at what speed, either high or low speed, a fault in this control module could be keeping the fan on if the thermal switch is still working okay.

No simple answer, but the idea that the AC controller is causing this sounds a bit wrong - but I could be wrong!

[sinenarockandroll]

Thanks RUN4MO, I'll take a look at the cooling fan control module.
The coolant temp. sensor has been changed to a new one and nothing changed.

[RUM4MO]

Coolant temperature sensor, you mean the one that supplies the engine ECU with coolant temperature and the temperature display on the dash with coolant temperature, probably a dual sensor - that has been replaced and the behaviour of the displayed temperature has not changed, that is not good, so that could mean a wiring issue or a dash pod issue, none of this should be making the fans run when they don't need to though, or does that car have some other wiring issues or earthing issues, this could take a lot of investigating.

If you were able to remove the AC control panel and unplug it and leave it off the car for a few days to see if that changed anything, that would help you to understand if it really was the AC control panel that was causing the fans running issue, then checking the part number of that control panel, see if you could buy a used one on ebay or from a car scrap yard - and fit it to your car. From what I remember from my wife's previous 9N Polo, there were only 2 screws holding that panel on, that panel is the controller for the AC system.

[sinenarockandroll]

I've had a try at the A/C control panel:

-> Drove the car for a while until it reached normal running temperature. The fans did not start.
-> Turned ON the A/C and both fans (big one and small one) started working
-> Turned OFF the A/C and both fans kept turning.
-> Turned OFF the engine and removed the key and both fans kept turning.
-> Removed the A/C dash panel - and both fans STOPPED.

Looks preaty like my problem is in the A/C dash panel unit isn't it??

I did the Climatronic scan and got two error codes:

2C1
318

I woulld happily get an A/C panel from a scrap yard but mine is reference 6Q0907044F and I can't manage to find the same one. Even on ebay or other I keep finding the same numbers but diferent letter, none of them ending on "F".

I'm a bit desperate now, thank God it is cold now in Spain and I can drive with the A/C panel removed

[RUM4MO]

I wonder what would have happened if you then plugged that AC control panel back in, what I mean is, I wonder if removing the 12V supply from it allowed it to "reset" and so it would be okay to use until you switched the AC chiller back on, I'm just curious I suppose.

Anyway, yes it looks like an AC control panel fault.

These 2 fault codes you got from the controller, have you tried to find out what they mean or refer to?

I have looked up a part listing for that car and it looks like your car was quite a late build one as "E" is the part number given with "F" being a suitable replacement.

So maybe try finding a slightly older "E" than the "F" fitted to your car as there should be more of them available from scrapped cars.

Edit:- when I looked up online, I found that a UK based used car parts was selling a "B" version which they claimed could be used to replace an "E" - so maybe consider a "B" if you can't buy an "E" version.