Radiator cooling fan problem? - Crasher/a8 tech - can you help?

**TouranDave** · 30-07-2008,09:35 PM

Crasher or a8 tech,

As you will know there are 2 radiator fans, I was just wondering do they come on together ? I thought the large one was for the engine and the smaller for the air con (really not sure) But when I did an output test in the engine module the large fan came on, I then did an output test in Air con and that also triggered the large fan. In fact I've never seen the small fan run!

What I'm thinking is if there is something wrong with the small fan, then maybe the ECU triggers the larger fan?

a8 tech, I found the air con module (thanks) its listed as 'Auto hvac' so that threw me!

Thanks, Dave

**Crasher** · 31-07-2008,11:00 AM

Seriously, I can’t see any way forward on this other then replacing the fans. It is such a problem that they even come with the cowling and are an updated part. Until you have changed these I can’t see how I can help you any further. The cowling/fan set is part number 1K0 998 455 and costs £198.96 inc. VAT and I have checked that this is the correct part number for your car using the reg number you sent me.

**kenney** · 31-07-2008,12:39 PM

Hi A fault with the engine management can activate the cooling fan,i have seen this a few times and it had nothing to do with the AC,so i would suggest a fault code read on the ECU.

**TouranDave** · 31-07-2008,06:22 PM

Crasher, I appreciate what you are saying, but I need to be more certain of what is causing the problem before I pay out the £198. Hence the questions, do both fans run together ? and are they low speed/high speed or a variable speed ?

This help would be great.

Thanks,
Dave

**Crasher** · 31-07-2008,09:52 PM

They need activation testing in outputs tests of the engine ECU using VAG-COM or similar. They run together or singly (as far as I have ever noticed) as determined by the engine and HVAC ECU’s and controlled by the control unit built into the main fan.

**a8 tech** · 31-07-2008,10:08 PM

The two fans can both operate at the same time with two stage speeds.The larger fan is indeed the control unit which can run at full chat if the first fan has failed.Crasher is correct in saying the fans fail and they where found to fail due to high internal resistance causing irratic operation or running on until the battery drained.It all depends on the wattage/amperage of the fans you have as to there operation cycle/speed but you should see the smaller fan kick in when the air con operates which you can check via measured values in air con and engine ecu.Or connect a amp clamp to the first fan and measure the current draw of the fan which isnt working.Again as crasher has also mentioned and i think you have checked the output test of the fans to confirm operation.The fans serve duel functions for cooling the engine and also the air con condenser.

**TouranDave** · 21-08-2008,09:29 AM

Crasher and a8 tech,

Just letting you know that after your last postings, stating the fan controller is built into the large fan, this I didn't know and it changed everything, I phoned VW and ordered the Fan set, that was 3 weeks ago and I still haven't got it! It turned out it was out of stock and they are waiting to get more in, this shocked me as it shows how big a problem this must be due to a faulty design, surely VW should realise this and fix it off their own back!

Anyway, I've just got to sit tight and wait for the call from VW!

Dave

**TouranDave** · 06-09-2008,06:46 PM

Hi Crasher and a8 tech,

I've got the new fans and fitted them, but it hasn't cured the problem just changed things a bit.
Now, 30 seconds after starting the car both fans run, but at a lower speed than before, so changing them has improved things, but its still not right.

Any ideas where to go from here ?

Thanks, Dave

**Crasher** · 06-09-2008,07:18 PM

You need a code read doing again to see if a sensor fault is firing them up. They were obviously fault but not the only fault.

**TouranDave** · 06-09-2008,08:54 PM

OK I've checked the fault codes, the only one that comes up is,
P1643 Please check DTC Memory of central electric ECU
I'm not sure what that means, but it has always been up. I don't know if its anything to do with my problem.

I did an output test for the fans, both tests, both fans came on.

Also, something I haven't mentioned before, again not sure if its relevant, but when the fans cut in (the car idling in neutral) the tickover revs rise to 1000RPM

So something is putting the fans on and increasing the tick over revs ?

Dave