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fan switch help

Discussion in 'A4/S4 forum(B5 Chassis)' started by mikeya4, Apr 8, 2009.

  1. mikeya4
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    mikeya4 Member

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    [Apr 8, 2009]
    Hi all,

    just got a 2.5tdi quattro and its running really well, very smooth but it has a couple of probs, the main one is that it over heats a bit under load, normal driving and it will stay at 90, get on the motorway and it creeps up.

    I have noticed the electric fan is not kicking in, please help???
    where is the fan switch?
    whats the best way to do the testing?
    i've heard theres a fan relay? is this likely to be faulty or is there a fuse?

    I have a manual for the a4 but its only for the 4cyl which makes it no good so have no idea where anything is on this engine

    please help

    thanks
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  2. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Apr 8, 2009]
    Fan switch is mounted on the Radiator, however the viscous one should still keep the temp down tbh Especially when on the move as the airflow through the rad from the speed would be much more than a poxy electric fan could give.

    I would be looking for more reasons, like a faulty waterpump or blocked rad
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  3. mikeya4
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    mikeya4 Member

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    [Apr 8, 2009]
    hi thanks for the reply, its had the water pump changes and when i put the heaters on it cools down which makes me think the circulation is ok? i think the aircon rad blocks most of the airflow to the rad, the viscous fan is working and when i slow down it cools down again. either way the 2nd fan isn't kicking in which i would like to fix

    thanks again
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  4. Nige P
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    Nige P Member

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    [Apr 9, 2009]
    Annoying isn't it! I have probs with my fan but not getting any help from here so far so will try to help you if i can.

    The electric fan should switch to slow when you switch on the aircon, if this happens then your fan should be fine.

    At the bottom left of the rad you should find the sender, mine is a green one with 4 pins, or it could be a black one with 3 pins. You can short out the pins in the socket which should fire up the fan in slow & fast speed. If this is OK then change the sender.

    There is lots of info on fans over on the uk-mkivs.net site which is similar to ours, search for "FAN PROBLEM - POLL SYNOPSIS"

    Have you checked if your rad is getting hot? could be a thermostat problem where it isn't letting the hot water through??
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  5. mikeya4
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    mikeya4 Member

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    [Apr 9, 2009]
    thanks for the reply, i've just been having a fiddle and turned the air con on and the fan didn't work, played with the wires by the fan and it worked, so its a dodgy connection by the fan, im gonna take it off tomorrow to have a closer look, maybe its repairable, thanks again
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  6. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Apr 9, 2009]
    Sorry if my reply was unelpful, I was waiting for the reply before delving too deep as internet diagnosis is not as easy as all that
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  7. mikeya4
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    mikeya4 Member

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    [Apr 17, 2009]
    Byzan A4, looks like you were correct, i've driven the car till it warms up then stopped, the top pipe going into the rad was hot but the rad was normal to touch(as in not even warm) this must be a blocked rad? the bottom pipe is warm but no where near the temp of the top one,
    is a blocked rad quite common?
    whats the best way to flush it?
    thanks
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  8. mikeya4
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    mikeya4 Member

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    [Apr 17, 2009]
    just reading up and getting a bit concerned,about the water pump, i was told this was done 5k ago, does anyone know which way the water pumps? as in if the top hose by the rad is hot does this mean its pumping through to the rad or the other way around?
    thanks
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  9. mikeya4
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    [Apr 18, 2009]
    one more question, does anyone know if the rads are the same throughout the a4 range, its proving hard to find parts for these 2.5s
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  10. Siena
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    Siena Active Member

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    [Apr 18, 2009]
    Sounds like a lazy water pump - the fan does nothing at constant speeds, so even if it was removed, it wouldn't cause overheating on the move.

    I believe the impeller is a metal one, but you never know...it could still be worn.
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  11. mikeya4
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    [Apr 18, 2009]
    like i said before, it was a new pump 5k ago, i just tried flushing the rad and when i put the hose pipe in the top of the rad it just trickles out the bottom, and when i put the hose pipe in the bottom nothing comes out the top. surely if the pump wasn't working properly the top hose wouldn't get hot? are they metal impellers on the 2.5s?
    cheers
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  12. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Apr 18, 2009]
    It sounds like a blocked rad, water should pass freely through the rad. Water flows from the bottom to the top typicaly. However if the Rad is blocked then it will be unable to push the water through.

    Have you tried breifly starting the car with a hose iff to see if it pumps at all? A bit pikey, but may prove that
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  13. mikeya4
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    mikeya4 Member

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    [Apr 18, 2009]
    nah, I haven't tried that. think im just gonna get a new rad. does it defo flow from the bottom to the top? I know its not an s4 but I was looking at the s4 self study thing and they flow from the top of the rad to the bottom.
    cheers
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  14. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Apr 18, 2009]
    not 100% if i am honest. All the smaller ones seem to, if i was colse to my proper PC i would take a look to be 100% for ya. When i mean flow, i refer to where the thermostat resdies, i may have crossed wires here
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  15. mikeya4
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    mikeya4 Member

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    [Apr 18, 2009]
    thats cool, thanks for your help, its just that the top pipe gets hot but the bottom one doesn't, thats what makes me think the water goes in the top pipe,
    cheers again
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