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  1. #1
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    Overheating when stationary (aircon/fan problem)

    Hi all... Back once again... As the tune says.

    Anyway, this time.... The car is overheating when I'm stuck I traffic. If I drive its fine, but starts to get hot once I stop.

    I've noticed there's 2 fans. The one on the passenger side spins kinda slowly all the time, regardless of engine temperature. The other fan I've never seen spin ( it's not stuck I can move it).

    Not sure if its related but my air-con does work but again, struggles when stationary. I can hear a click from under the car but it seems to turn off after a minute, only to then itself on again. Then it just repeats. So I'm confused to whether its a fan problem, air con problem or other?

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    tedward's Avatar
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    Big fan is for engine cooling, smaller one should kick in as soon as your air con is switched on.

    Could be a relay or fuse related problem. Also fans do get more fragile with age could be seized.

    Need to leave it running no ac on and see if the main fan kicks in when the engines nice and hot (will take maybe 15 mins) and then have someone turn your ac on and stand and see If the other fan kicks in.

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    I guess the fan isn't kicking in for some reason. Could be a fuse?

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    Overheating when stationary (aircon/fan problem)

    Quote Originally Posted by tedward View Post
    Big fan is for engine cooling, smaller one should kick in as soon as your air con is switched on.

    Could be a relay or fuse related problem. Also fans do get more fragile with age could be seized.

    Need to leave it running no ac on and see if the main fan kicks in when the engines nice and hot (will take maybe 15 mins) and then have someone turn your ac on and stand and see If the other fan kicks in.
    Fan never kicks in. It just spools at constant speed regardless of temp. Also the other fan (driver side) definitely doesn't come on, that's confirmed.

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    Overheating when stationary (aircon/fan problem)

    Quote Originally Posted by TqsScott View Post
    I guess the fan isn't kicking in for some reason. Could be a fuse?
    Good shout. I'm gonna check, they under the steering column somewhere?

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    Quote Originally Posted by Paddymph View Post
    Fan never kicks in. It just spools at constant speed regardless of temp. Also the other fan (driver side) definitely doesn't come on, that's confirmed.
    You say you can turn it freely by hand ( the non working one).?

    If so it's an electrical/ relay problem.

    Start with the basics, main fuses and move onto relays. Failing that you could try sending a direct feed to the currently non working fan just to check it's actually still alive and able to spin. ( don't lose a finger in the process)!

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    tedward's Avatar
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    Just remembered b5s have a viscous cooling fan so the main one that cools your engine is turning all the time.

    Sounds like your problem is just ac fan related. Sorry for the curve ball!

    Have you ever had the ac topped up or checked for ac gas leakage or even if there's any in at all?

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    Overheating when stationary (aircon/fan problem)

    No I haven't. And this is what I'm thinking.

    Would that cause the actual engine temp to rise? Why doesn't the main fan just go faster?!

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    Quote Originally Posted by Paddymph View Post
    No I haven't. And this is what I'm thinking.

    Would that cause the actual engine temp to rise? Why doesn't the main fan just go faster?!
    Pretty sure it needs gas to work, they usually have a sensor no gas no fan. Think quick fit top up for around £40-£50.

    Although dont rule out electrical gremlins, but at the end of the day if you have no a gas there's no point in the fan kicking in anyway.

    The main fan will turn more quickly if your on the move, it's run from the engine so keeps in time with engine speed.

    Could be a water pump issue or blockage?

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    Do your heaters work? I had an old metro with a simular problem. The fan didn't kick in as it had blockage and thought things were still cool when it was overheating.

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    i think you have two seperate issues
    my a/c fan didnt work for a year but the car never overheated (just knocked a/c off when stuck in traffic)

    id be looking at pump or rad
    kev
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    Overheating when stationary (aircon/fan problem)

    Pretty sure no blockage as its had a new thermostat and coolant.

    Heaters work fine. Just tested aircon and it is cool...?

    Oh, and I can see coolant being pumped back into the header tank so pump must be ok?

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    tedward's Avatar
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    So is it just the gauge reading high?

    Or is the haeader tank actually bubbling over in traffic or when hot enough to do so?

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    Overheating when stationary (aircon/fan problem)

    Gauge. But it is gettig hot, confirmed by AC trick. Not boiling over though... Could it be coolant temp sensor?

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    tedward's Avatar
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    Possibly, as it's only a few quid to change, do it.

    There will be a million how to dos if you google it.

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    Overheating when stationary (aircon/fan problem)

    Yep.

    Last question. Where are the relays? They in the engine compartment under the windscreen?

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    Overheating when stationary (aircon/fan problem)

    Scrap that. It's in the footwell?

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    tedward's Avatar
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    Not 100% sure but I would say under the steering coloum area or possibly behind the glove box??

    Again google will help as I'm sure you are not the first.

  20. #19
    "Stick a V8 in it!"

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    Non-AC A4 1.8T's didnt even have the second electric fan, just the one viscous unit.

    My car has no viscous, just the one small electric fan, and i've never seen it climb past 100c in traffic.

    maybe the viscous coupling has had it?

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
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    Overheating when stationary (aircon/fan problem)

    Not sure. I can't figure it out. Checked the fuses under the dash and all seems ok.

    It's a 1.8 non turbo by way. Air con is deffo working its nice and cold. But no fan? And temperature is still rising whilst parked...?

    Aghg. ANOTHER garage trip

  22. #21
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    Quote Originally Posted by Paddymph View Post
    Hi all... Back once again... As the tune says.

    Anyway, this time.... The car is overheating when I'm stuck I traffic. If I drive its fine, but starts to get hot once I stop.

    I've noticed there's 2 fans. The one on the passenger side spins kinda slowly all the time, regardless of engine temperature. The other fan I've never seen spin ( it's not stuck I can move it).

    Not sure if its related but my air-con does work but again, struggles when stationary. I can hear a click from under the car but it seems to turn off after a minute, only to then itself on again. Then it just repeats. So I'm confused to whether its a fan problem, air con problem or other?
    I think you may have 2 separate problems here. Common causes of overheating with no other obvious signs is waterpump, well documented on here. Basically the plastic impeller comes adrift internally so could well be the cause if it hasn't been changed, perhaps more noticable when in traffic, no air flow to cool the rad.

    The secondary electric fan is for the aircon. I believe it should come on when the aircon is switched on regardless of temperature. It is also a common failure. Had this on my A6, aircon seems to be cooling fine whilst driving but less effective when stuck in traffic as there is no airflow to cool the rad. I bought a new fan, I stripped my old one down and the carbon brushes were worn down. I did manage to get it working but a new fan\brushes would be the long term solution.

    You could try running 12v straight to the fan (what I did) this would tell you straight away if its at fault.

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    Overheating when stationary (aircon/fan problem)

    Should my main fan not speed up though when it's getting hot?

    Good advice so far tho, thanks all

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    "Stick a V8 in it!"

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    Yes the main fan has a viscous coupling which should "lock up" when the engine reaches about 100c.

    When the water pump failed on mine, it was fine at idle. But engine RPM's above 2000 saw the temp shoot up very quickly. My reasoning is that while the impeller had cracked, it was still sitting on the shaft. At low RPM's it was gripping the shaft just enough and managing to stay spinning, however when the RPM's increased the resistance on the impeller increases and the grip on the shaft isnt enough so it "lets go" and stops spinning.

    What temperatures have you been seeing? Use channel 49 on the climate control diagnostic for an accurate reading.

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
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    Overheating when stationary (aircon/fan problem)

    I've had a golf where exactly that happened Aragon. So I don't think it's the pump. Mines the other way round, overheats when I'm stopped. Plus I can see the coolant circulating back into the header tank so it must be pumping? Right..?

    49' trick shows all the way upto 115 then I bottle it and kill the engine. If I drive for only 1 minute it cools down instantly.

    Intesrestingly. I've just hit the little fan with a hammer and its spun into life?! Gave off loads of what looke like metallic grey dust / residue.

    Temps are still going up tho...? Currently sat with bonnet closed, both fans now spinning (although not very fast) and its increasing ... What's the operating temps for fans normally?

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    Overheating when stationary (aircon/fan problem)

    😃😃😃😃😄

    Ok I'm getting somewhere now. The temp is going up as the fan (smaller one on the drivers side) IS stuck.

    When I hit it it spools and the temp drops. But it sticks a bit an sooner it later stops.

    I've WHALLOPPED it again an the fan has come on FULL force dropping temps to low 90's. it seems to be coming on as it should be.

    It APPEARS, and I use the term lightly... That is is fixed?!?

    If in doubt.... Smash it with a hammer!?
    Last edited by Paddymph; 28th September 2012 at 13:23.

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    the metallic grey dust sounds like dust from the brushes in the motor. You could try taking off the fan and dismantling/cleaning etc and even put new brushes in ( if you can find some - try somewhere like ebay, where I found brushes for an old alternator !! )
    I read fairly recently that somebody did this with an A6, dealer wanted over £200 for a new bit and all it needed was a couple of hours , fiddly but relatively straightforward work, and a few pounds for brushes!!
    Other than that get a 'newer' one from breakers or where ever, or perhaps somebody here has one ??
    ChrisG

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    "Stick a V8 in it!"

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    I think your viscous coupling on the main fan is dead, plus the electric fan was clearly broken.

    If you want to test the coupling, start the engine and using a screwdriver handle on the rim of the fan (dont stick it in the spokes!), note how much force it takes to stop the fan. It should be fairly easy to bring it to a stop.

    Then once the engines up to 100c, try again.

    At 100c it should be VERY difficult to stop the fan if the coupling is working properly.
    Last edited by aragorn; 28th September 2012 at 16:47.

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    Overheating when stationary (aircon/fan problem)

    Can anyone clarify which is my main fan then?

    Expensive fix? I'm presuming your saying its not going to last? Seems ok this afternoon so far.... 😕

  30. #29
    "Stick a V8 in it!"

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    The main fan is the one that spins all the time. It has a fluid filled coupling, which when at normal temps acts "loose" and doesnt transmit much force to the fan. When the temp climbs its supposed to lock up, and will spin much more powerfully.

    The electric fan is there to assist the main fan. It has two speeds, low speed comes in as soon as you turn the AC on, or if the coolant gets upto about 98c, then high speed comes in if the coolant gets over 105.

    On my car, i removed the main viscous fan, and only have the electric one, and TBH i've never even seen it engage high speed. Low speed kicks in at 98c and the temp generally stays around there. With a working viscous fan you wouldnt need the electric fan at all.

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
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    Overheating when stationary (aircon/fan problem)

    Legend. That's answered my questions. Thanks

  32. #31
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    Quote Originally Posted by aragorn View Post
    With a working viscous fan you wouldnt need the electric fan at all.
    I would have to disagree with you on that, without the secondary fan your air con will not work efficiently when stationary. If you are short on funds its worthwhile stripping the motor and cleaning out the dust. The most common cause of failure of this motor is the carbon brushes either wearing out or becoming stuck in their guides. Your hammer method proves it can still work!

    It should be possible to find replacement bushes, I would have done this on mine if I hadn't already bought a new fan.

    (BTW it was probably my A6 Kingfisher had read about in Audi Car recently)

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    Ah yes, indeed it was ( I read so much stuff I cannot always remember where I get things from !!)
    ChrisG

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    "Stick a V8 in it!"

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    Quote Originally Posted by mwarrey View Post
    I would have to disagree with you on that, without the secondary fan your air con will not work efficiently when stationary. If you are short on funds its worthwhile stripping the motor and cleaning out the dust. The most common cause of failure of this motor is the carbon brushes either wearing out or becoming stuck in their guides. Your hammer method proves it can still work!

    It should be possible to find replacement bushes, I would have done this on mine if I hadn't already bought a new fan.

    (BTW it was probably my A6 Kingfisher had read about in Audi Car recently)
    AC might cut out sure, but the engine will stay perfectly happily within its normal temperature range, which was my point.

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
    2000 A4 1.8T Sport Quattro Saloon, Black-ish
    1997 S4 - PPC £999 Challenge Track Car Build
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