Fan constantly running, draining battery......

[catso]

2004 A3 3.2 - Went out to car tonight to find the fan was running, it had been some 2 hours since last used. Car started OK but was sluggish turning over due to battery being low, drove OK but the fan was running constantly.

Got back home & the fan wouldn't stop, I left it for an hour or so but the fan was still running but slowly by now as the battery has run down and the garage is full of 'electrical' smelling smoke.

I have disconnected the battery (which is a job in itself due to the location) to stop the fan and put the battery on charge so that it might be start-able in the morning.

I am thinking that the problem is some sort of thermostat/switch that brings the fan on that has failed but does anyone have any ideas where/what to look for? could do with not having to take it to a dealer.

TIA

Edited by catso on Thursday 7th May 01:25

[BigAustin]

follow wires from fan motor to the sensor
On alot of cars it is a sensor screwed into the top of the rad, not sure on the A3 though. It could be in the engine block too.

You may be able to get a non genuine one from a motor factor.

[catso]

Thanks for the reply, problem is that the engine bay is very cramped, especially in the radiator area and everything is hidden behind plastic covers with very few wires on show.

Would be nice to know specifically where the sensor is before I spend hours stripping off the covers etc only to find I'm looking in the wrong place.

[hman]

ring up audi, the parts departent are normally very helpful.

[cuprabob]

I'm not sure about the 3.2 but I know other VAG models (1.8T) have a fan controller built into the fans and they have a reputation of failing needing the whole fan to be replaced. IIRC the temperature signal comes via the ECU.

The normal failure mode is for the slow speed running (with air con on) to fail causing the fans to pulse and eventually blow a fuse. This is caused by a resistor in the controller burning out although from your symtoms it sounds as if something has short circuit keeping the fan on all the time.

In the short term you could just remove the fuse to the fan to stop the battery draining but keep a very close eye on the temp gauge as there is a high risk of overheating without the fan.

[catso]

cuprabob said:

I'm not sure about the 3.2 but I know other VAG models (1.8T) have a fan controller built into the fans and they have a reputation of failing needing the whole fan to be replaced. IIRC the temperature signal comes via the ECU.

The normal failure mode is for the slow speed running (with air con on) to fail causing the fans to pulse and eventually blow a fuse. This is caused by a resistor in the controller burning out although from your symtoms it sounds as if something has short circuit keeping the fan on all the time.

In the short term you could just remove the fuse to the fan to stop the battery draining but keep a very close eye on the temp gauge as there is a high risk of overheating without the fan.

Interesting but sounds expensive

I've now recharged the battery but as soon as I connect it the fan runs continuously. There are 2 fans a large one on the left (nearside) and a smaller one on the right, it's the larger one that runs, I took out the fuse that claims to be for the fan but it still runs? however even if it did stop it the fuse is also (according to the manual) for the ignition coil?

I really didn't want to pay a dealer £100+ (and probably double that if it needs a new fan) but it's not looking good.

Thanks for the info.

[Tame Technician]

Its defiantly the fans, we do loads of them for that fault effects 2.0tdi, 1.8T and 3.2.

You get a kit with both fans and a modified cowl. Parts are about £200 + fitting.

Its very difficult from the parts information for the parts guys to pick the right one, we usually order the two different options and check them, sending the other one back, almost every time we have ordered just one, the wrong one comes in.

[catso]

Tame Technician said:

Parts are about £200 + fitting.

Now you have upset me but thanks for the info, is there an easy way to stop the fan when the car's stopped? (fuse or something) as disconnecting the battery is a bit of a job as you'll know and if I park up anywhere the battery will run flat.

Otherwise I'll just have to charge it and connect it to drive to the garage, unless I can get the bits and DIY it?

[3sixty]

Had a similar thing, albeit on my Mk4 golf. I'm not sure whether the 2004 A3 is in the 'Mk4' era of Golf or Mk5, but if it is the Mk4 era I presume it will be a similar story.

http://uk-mkivs.net/forums/t/59897.aspx All the testing and information is on there.

Apparently, the reason they will fail is a design fault of VW and all other cars from the big Audis down to the Passats with climatronic. They use a fan speed controller, that utilises "pulse width modulation" to control the fans and thus negates the need for resistors in a high current circuit.

[catso]

3sixty said:

Had a similar thing, albeit on my Mk4 golf. I'm not sure whether the 2004 A3 is in the 'Mk4' era of Golf or Mk5, but if it is the Mk4 era I presume it will be a similar story.

http://uk-mkivs.net/forums/t/59897.aspx All the testing and information is on there.

Apparently, the reason they will fail is a design fault of VW and all other cars from the big Audis down to the Passats with climatronic. They use a fan speed controller, that utilises "pulse width modulation" to control the fans and thus negates the need for resistors in a high current circuit.

Interesting, although the problems on there seem to be mainly fan running at the wrong speed - mine is constantly running at what I think is the high speed even with ignition off, although maybe it's the same failure that causes both problems?

I've just taken all the (known to me) fuses out, one at a time and it still won't stop, are there any 'hidden' fuses or does the fault bypass any fuse?

Edited by catso on Thursday 7th May 14:16

[Tame Technician]

The fuse will be a large one, 30 amps ish and its in the fuse box under the bonnet next to the battery, you have to slide the cover off of that one. SHould even be labeled in the handbook shown with all the other under bonnet fuses.

Taking it out will prevent the battery going flat while the car is parked, but be sure to put it in before you set off, as getting stuck in trafic or anytime the engine is running and you arent moving through the air will have you overheat and damage the engine.

[catso]

Tame Technician said:

The fuse will be a large one, 30 amps ish and its in the fuse box under the bonnet next to the battery, you have to slide the cover off of that one. SHould even be labeled in the handbook shown with all the other under bonnet fuses.

Taking it out will prevent the battery going flat while the car is parked, but be sure to put it in before you set off, as getting stuck in trafic or anytime the engine is running and you arent moving through the air will have you overheat and damage the engine.

Battery is in the boot, under the floor. As for the fusebox in the engine compartment, the manual says 'F8 Radiator fan 10A' and 'F54 Radiator fan, output stage 50A' (but there is no F54?), I have actually taken every fuse out of that box and every fuse out of the box at the end of the dashboard (one at a time) but the fan still runs, which seems odd?

Either way fuse removal is only a temporary option until it's fixed, at the moment the battery is disconnected so using the car is not an easy option so I've been using the bike today .

Looks like my local dealer may be getting it shortly.....

[Tame Technician]

I forgot the battery is in the boot on 3.2's. None of the fuses in the end of the dash have anything to do with it.

Did you take all the fuses out of the engine bay fuse box, one of these should stop it.

Failing that you need the find the 50amp mega fuse it speaks of. This will have to post at either end of ot with 2 10mm nuts, you need to take the one that goes to the fan off by removing the 10mm nut. Again should be on or very near to the underbonnet fuse box.

[Tame Technician]

should look somthing like this.

This is off a 1.8T seat so not identical but very nearly.

http://i566.photobucket.com/albums/ss107/rikwheele...

[catso]

Tame Technician said:

I forgot the battery is in the boot on 3.2's. None of the fuses in the end of the dash have anything to do with it.

Did you take all the fuses out of the engine bay fuse box, one of these should stop it.

Failing that you need the find the 50amp mega fuse it speaks of. This will have to post at either end of ot with 2 10mm nuts, you need to take the one that goes to the fan off by removing the 10mm nut. Again should be on or very near to the underbonnet fuse box.

Thanks, I reconnected the battery and tried all the fuses again, none would stop it but I unbolted the cables/fuses on the front like in your picture, which I hadn't done before (there are 3 x 80W, 1 x 50W, 1 x 200W and 2 cables with no fuse) one of these (80W) stopped the fan.

Then I reconnected it and the fan 'jumped' a couple of times and then stopped, now it doesn't run, only thing is I think it doesn't run at all even when hot. I went for a drive to see if I could get it running and it wouldn't, neither does the other (smaller) fan although I'm not sure when they should run and the car wasn't overheating but they don't run with the A/C on either, should they?

I'd like to think it's fixed but I suspect that the fan might now be knackered which may be a different problem but the solution is probably the same. Phoned my local dealer (that I bought it from) and the quickest they can look at it is next thursday!

Also I now have a yellow 'engine' light on, although this maybe because I pulled one of the relays out whilst it was running (the grey R4 with the number 458 on it) that seems to stay active after the engine is stopped and cause the other 'whirring' noises in the engine.

Edited by catso on Friday 8th May 16:20

[Tame Technician]

That relays was probably for the Additional electric water pump.

Make sure when it goes in you explain the fault was only with the fans, and you removed fuses to try and stop it. It was the removal of the engine bay fuses that caused the warning light to be on, something loosing its power has falsely generated a fault code. Thats why the Audi centre need to know, or the technician could be misled by these spurious codes.

Regard the fans not working at all any more, when you have a moment run the engine for 15 20 mins or so until its up to temperature. KEEP A CLOSE EYE ON THE GAUGE. When it gets hot the fans should run. If they dont, then they have completely given up and you will have to be carefull when driving the car until it is fixed.

It is the control module built into one of the fan motors going faulty than causes the fan to run on all the time. Possibly disconnecting and reconnecting the power has killed it off completely.

[catso]

Tame Technician said:

It is the control module built into one of the fan motors going faulty than causes the fan to run on all the time. Possibly disconnecting and reconnecting the power has killed it off completely.

That's what it would appear to have done as neither fan will now run - but at least the battery doesn't run down.

So to update I have used the car and whilst it hasn't run any hotter than the normal 90 degrees (mid position on gauge) I'm pretty sure the fans don't work and when I try the A/C it tries to cool for about a minute trying but then switches itself back to econ - neither fan runs at this time.

I've not got the engine hot enough to be a problem but it seems that the fans are knackered now although the yellow engine warning light has now reset itself and gone out and everything appears to be working as normal again (except the fans).

I suppose it'll be OK on open roads etc but need to avoid city traffic and hot weather.

[catso]

Update - Fans had completely failed, after running continuously the controller burnt out so had them replaced, dealer 'found' that the radiator also had a leak so whilst everything was apart had that changed (actually had been occasionally topping up coolant) so it cost a little more than expected at a tad under £540, the fans alone would have been £380.