Jetta 5 Fan

[grhmallan@live.co.za]

I have a 2008 Jetta 5 2.0, the small fan was not working and the main fan came on from start and would stay on, I've changed both sensors now, its also just had a major service, I also have now changed both the main and small fan yesterday, the fans are now still coming on from start however when I turn the car off they turn off. They not blowing as hard as they were but surely they should only come on when needed not from start, anyone with a solution to this problem...? My bank account is starting to be feel the punch of trying to solve this problem and my frustration levels are rising


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[panic-mechanic]

Is your climate control switched on.? Do they still blow when it is switched off. I have had quite a few that lets the fan run a while when you have just started it. It stops and then comes on again when hot. As long as the car is operating and not overheating I would not worry about it much. Or are you saying they are running permanently?

[grhmallan@live.co.za]

I checked the climate control, it is off... I had another guy do a diagnostic test and one fault was picked up being a sensor I changed which doesn't make sense. After clearing the fault it worked perfectly for half an hour then back to its problem again... The fans run from starting the car until ignition off. Someone said I should check my aircon gas.


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[panic-mechanic]

If the climate control is off the aircon will not run and thus th fans will not be kicked on by that so not aircon gas causing it.
If the water temp sensor is stuffed yes the management will run the fans all the time to protect the engine.

[VGTI]

I had something similar on the SEAT Altea (same platform as Jetta 5). Turned out to be a faulty ambient temperature sensor. Check if the temperature shows on your OBC. If you see just lines it s not working.

Worth a try...

[kylebassani]

I checked the climate control, it is off... I had another guy do a diagnostic test and one fault was picked up being a sensor I changed which doesn't make sense. After clearing the fault it worked perfectly for half an hour then back to its problem again... The fans run from starting the car until ignition off. Someone said I should check my aircon gas.


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Is there no way the sensor can be checked to ensure it is working correctly?
Unfortunately even if we buy new parts, on the odd occasion a faulty part does pop it's head out every so often.

[Kyle]

Came for Jetta 5 appreciation thread, leaving disappointed.

[panic-mechanic]

Yes in vcds going to single reading blocks or advanced you can see the actual reported temperatures and check that they look reasonable.
You can't do that with generic obd scanner though. Has to be vcds/odis/cas/obd11 or similar.

[Ncuthu]

I hv a same problem with my jetta 5 2007, 2l. Did the diadnosis and its shows a "faulty radiator sensor". I changed both sensors, i bought a new fan and changed the thermostat but still doing the same. And now i jst discovered that the big water pipe on the left, the one close to the watercbottle stays ice cold while the other big water pipe on the right close to the bettery is hot. # Strange

[grhmallan@live.co.za]

Ncuthu, it's very strange, i replaced the one sensor again on Saturday, I even replaced it with an original one, its slightly better however the fan still comes on from start, my next option will be to take it to an auto electrician and see if it's not a wiring fault that's giving mixed signals...


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[ThatBloke]

Shame man, you must be so pissed by this stage, nothing worse than sinking big wads of cash into a problem and getting absolutely no joy.

If you work back from the fan, what can trip the fan or trigger it on/off, is there no way to isolate the fan just to core engine cooling duties?

[panic-mechanic]

Fans are switched on by the ECU via a controller built into the fans that tells it at which rate to run. So you need vcds to do output tests and see if the fans are coming on when the management tells them to.
If they do then the fans are ok but that the management uses to measure the engine temp is not OK and it thus switches them on by default to save the engine.
this is one piece of diagnosis you are not easily going to do without vcds and some knowledge.


NCUTHU. a cold pipe means the new thermostat is also not working or you have an airlock. Remove the cap when the engine is cold and let it idle to temp while filling. once it shows 90 on the cluster and the bottom hose warms up close the cap. If the bottom hose never warms up the new thermostat is also not working.

[VGTI]

Did you guys do what I suggested above? It is a small and easy test and might just be your issue...

I can only assume but it goes along with what Panic is saying...

The management uses the ambient temperature input and if it doesn't get input it will revert to a failsafe option of switching on the fans whether it is hot or not...