Fan/Relays under battery, A3s TDi 2004 BKD

**RichyA3** · 11-05-2015,08:10 AM

Hi All, I have an A3s TDI 2.0l 04 reg BKD eng no (it also has 8P1, so is the engine code BKD 8P1 or BKD or 8P1), I have the age old radiator fan staying on problem..... when I take the fuse (f8) out of the fuse box the fan stays on, it will only go off if i disconnect the battery or the plug on the fan itself, I have changed the coolant temp sensor (as my local garage scanned it and said that was a permanent fault) but thuis made no difference, I am now assuming it is the module in the back of the rad fan's casing that is faulty and will need to replace the whole assembly (both fans etc), however, I have recently been told that one of the relays underneath the battery (have to remove battery to access them) also controls power to the fan??? is this correct? and what do these relays do? (I know how they work inside but not what these ones are for).

Any help/advice would be much appreciated, Many thanks.

Richy

**UVB** · 12-05-2015,10:03 AM

I know someone who has just had the exact same issue with the smaller of the two fans coming on. He says he's found a replacement sensor for something like £5 and has booked it into his local garage to get replaced this Thursday. Will keep you posted on it in case that solves it for him.

**RichyA3** · 12-05-2015,09:03 PM

Hi UVB, the smaller fan is air con fan, it is linked to the rad cooling fan, it would be interesting to know if the new sensor resolves it. Thanks.

**kanecullen89** · 12-05-2015,10:29 PM

Your engine code is just BKD.
The generation of your car is 8P1

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**RichyA3** · 13-05-2015,10:30 AM

Thanks for the info

**Crasher** · 13-05-2015,10:31 AM

There are no external controllers on this system, the fan controller is in the large fan.

**RichyA3** · 13-05-2015,11:13 AM

Hi Crasher, So, the control unit in the rear casing of the larger cooling fan is the only "controller" in the system and there are no other relays at all?

Many thanks for your advice

**Crasher** · 13-05-2015,04:08 PM

The controllers SDC code is J293 and this is inside the big fan. The J293 receives a feed from an 80A fuse called SA3 and this is direct to the battery feed in the engine bay fuse box. There is a feed from the line 30a relay J317 that goes to fuse SB8 and this is the power for the V157 intake flap motor as well. There is a 6mm thick brown earth wire and the feeds to the V177 smaller fan. The fan is controlled from the engine ECU along a signal wire. If this line is broken but the fan still sees a power feed on the line 30A wire from fuse SB8, the fan controller assumes the engine is running but as it does not know the temperature, it runs at max just in case but will stop as soon as the feed from fuse 8 is removed. If the fans run with the ignition off and there is definitely no feed from fuse 8, that is the fan controller for definite, the fans running only whilst the ignition is on can be the controller or a loss of signal from the engine ECU. The usual solution is the fan upgrade kit from VAG which is part number or and costs £291.78. These are available for less fro Euro, part numbers 213440560 or 213440290 respectively and the quality of these is fair, not brilliant.

http://www.eurocarparts.com/search/213440560/p/home

http://www.eurocarparts.com/search/213440290/p/home

**RichyA3** · 14-05-2015,10:44 AM

Hi Crusher, Many thanks for the info, I didn't think there was a relay (but had been told there was), I think it is a problem with the fan itself but just wanted a little more assurance before replacing them. Thanks again, Richy.

**UVB** · 14-05-2015,12:28 PM

Looks like the news at our end isn't so good either; the person I know has had his car scanned and the sensor checked this morning; all comes out ok so it looks like it is the fan unit as per Crasher's post above.