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A4 (B6) fan staying on when engine is off.

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by paulfromwire, Aug 10, 2010.

  1. paulfromwire
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    paulfromwire New Member

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    [Aug 10, 2010]
    I have an A4 (B6) 1.9 Tdi 2002. I went to work on Saturday & finished 8 hours later. I came out to the car to find the fan on. I went home (20 miles) then planned to drive up north. I found that the battery was so flat I couldn't unlock the car. I jump started the car & made the 160 mile journey with no problem however the fan came on approx 20 minutes after I stopped the engine. I've read some other forums & they were saying that this is due to water ingress into the ECU box & soaking the relays. Can anyone point out where the ECU box is & can this problem be related to the recent recall of B6's due to blockages in the plenum chamber?
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  3. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Aug 10, 2010]
    The engine ECU is in the engine bay to the left of the brake servo & battery, behind the steering wheel.
    To gain access will need to remove the windscreen wipers and the plastic water deflector beneath them.
    You can then get access to the torx screws securing the plenum chamber lid.
    Under the lid is the Engine ECU and some relays. If you have an auto-gearbox it's ECU is below the engine ECU.

    Just checked the circuits and there are no relays in the plenum chamber for the fan.
    There is a wire from the Engine ECU to the fan control unit (Heat sink unit on the fan itself) - colour: red/white.
    This is based on petrol models so assuming it's the same for diesel.
    PM me if you want the circuit I have.
    Last edited: Aug 10, 2010
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  4. paulfromwire
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    paulfromwire New Member

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    [Aug 10, 2010]
    Terrific mate & many thanks for your help.
    I was totally amiss as to where my ECU was as Warrington Audi agreed with you but Bristol Audi said it was under the passenger seat.
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  5. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Aug 10, 2010]
    Bristol are talking about the convenience module (electric windows/mirrors/central locking/alarm etc.) which is as they say mounted on the floor under the passenger seat.
    This unit can suffer from water ingress through the air intake on the right of the battery where the pollen filter is.
    Check for water around the base of the battery - drainage holes could be blocked if there is water visible.
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  6. paulfromwire
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    paulfromwire New Member

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    [Aug 12, 2010]
    Thanks again Woorlord. I've already had the problem (that many others have had) with ingress of debruis and water entering the brake servo & causing it to fail. Audi have sent recall letters to many people asking them to bring in their vehicles to be checked for debruis etc.

    Reading posts from your good self (& other forums) I have inspected the inside of the ECU housing to discover that the box was flooded which has totally caused havoc with the relays as now the car is a non-starter, my mate came out in his wrecker & took it back to his garage. Got a call from him 10 minutes later telling me that all of the relays were shot, one of them being the relay to the lift pump. I wonder if the can be linked to the recent recall of this vehicle? (I will be taking advice from trading standards tomorrow)
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  7. vinesh
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    vinesh Member

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    [Aug 12, 2010]
    Just checked my car.

    Battery area full of water - just below the brake servo. I did notice water leaking on the (near the mudflaps).

    As its dark, I cannot remove the battery. As a workaround I got a hose pipe and sucked the water and let it run.

    I will remove the battery on Saturday and remove the rubber drain plug.
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  8. murran
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    murran Active Member

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    [Aug 12, 2010]
    this is soooooo common rotting leaves clogging the rubber drain grommits causing an on board swimming pool. the recall is simply to remove the drain grommits!

    before you go removing the battery... do you know your radio code?
    #7
  9. vinesh
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    vinesh Member

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    [Aug 13, 2010]
    I believe you only need the radio code when you move the headunit to another car.

    I replaced the battery on my old 1.9tdi and it did not ask for the code.

    Might be wrong on the 2.5tdi.
    #8
  10. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Aug 13, 2010]
    Correct - your car learns the radio serial number and stores it, (I think), in the instrument cluster.
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