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temp gauge acted a bit odd

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by deanski, Nov 27, 2010.

  1. deanski
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    deanski wax on, wax off

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    [Nov 27, 2010]
    I was being a bit of a nancy at work last night as it was freezing cold i left my car running to warm up. i left it a good while and the temp gauge was at 90. i stuck the heaters on for a few mins and then it plummeted to 70? any ideas gents? it got back upto temp a few mins later.
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  3. PaulTheo
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    PaulTheo Member

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    [Nov 27, 2010]
    Thermostat a bit slow or the temp sensor I have had problems with both in the past.
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  4. deanski
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    deanski wax on, wax off

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    [Nov 30, 2010]
    so i drove home tonight (30 mile trip) and when I put the heaters on full with the engine plenty hot, the temp plummeted to almost cold and the car was running like a bag of ****. stuttering and hardly revving. temp sensor? :unsure:
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  5. paul20v
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    paul20v Audi fanatic

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    [Nov 30, 2010]
    Thermostate
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  6. simon.m
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    simon.m Active Member

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    [Nov 30, 2010]
    i had both my temp sensor and Thermostate done about 10 mths ago on mine and when driving /school run for the first say 15 mins it gets to 90 if i put the heater on hi it will cool the engine down but if i leave it just a weeeee bit longer to heat up properly say 20mins it will stay at 90 no matter what
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  7. deanski
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    deanski wax on, wax off

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    [Nov 30, 2010]
    would a dodgy thermostat make the car run rough?
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  8. scott b
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    scott b Active Member VCDS Map User

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    [Nov 30, 2010]
    mines the same, even sat in traffic with the heater on full it will take the temp down to 70, but even in my works van, when the van has been running for ages then leave it running with the heater on full, the temp will drop
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  9. paul20v
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    paul20v Audi fanatic

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    [Nov 30, 2010]
    If it takes it down too cold yes
    as what happens is the temp sensor tells the ecu that more fuel is needed when it actually isnt .
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  10. stu_m
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    stu_m Active Member VCDS Map User

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    [Dec 1, 2010]
    im having a few probs on mine with temp

    its taking ages to warm up to 90 but once its there it will sit there all day

    when i took it for MOT the other week i drove there and left it running for a bit as it was slightly over 70°c when i pulled it into the bay for MOT it was still not at 90 and when reved for the emmisions the temp dropped well below 70 again!!

    ive done both my sensor and stat about 6 months ago im going to change my stat and seal again to see how it goes it could be a slow stat or duff seal
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  11. simon.m
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    simon.m Active Member

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    [Dec 1, 2010]
    let us all no how you get on stu_m ;-) as mine is the same its all new yet if i just turn the car on and leave it on tick over it gets worm but no where near 90 till im driving
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  12. ScottD3
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    ScottD3 I want your faulty electronics

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    [Dec 1, 2010]
    Same issue here but with a B5.
    It will take a long time for the temp to move off 0 and even then it wont get full to 90 untill a long drive.
    If I stop and let the car idle it will drop down to 70 or even 0.

    I will have to try a new thermostat and sensor by the sounds of it.
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  13. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Dec 1, 2010]
    Diesels run very cold anyway, so if driving at low loads with lots of heater its entirely possible for it to take an age to warm up. At idle a diesel will often cool down they produce so little heat.

    The other issue is the temperature guage lies, and displays 90 as soon as the temps over 80c. Its entirely possible (if it was a derv) that you;d left it running for an age (wasting diesel and contaminating the engine internals with partially combusted fuel/soot) and it hadnt got to 90 at all, but was infact just on 80c, then when you cracked the heater open it dropped a few degrees and the temp appeared to drop from 90 to 70 when infact the actual engine temp only went from 80 to 75.

    If its a petrol its certainly not normal, and i'd be looking at changing the stat pronto. If its a derv, i've no personal experience, but i'd still expect it should stay at 90 so long as your actually driving it, rather than just sitting idling.

    If the stats never been changed, then i'd be doing that first, as contrary to popular belief its more likely to fail than a solid state electrical sensor.
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  14. simon.m
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    simon.m Active Member

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    [Dec 1, 2010]
    well im told diesels will cool of on tick over and as there is alot of ppl on here and the cars are all doing the same id say its normal i just did the school run takes 20mins in stop start trafic and it hit 90 just as i was turning into my road and i think that is right in this weather.
    was wrighting this as you did yours above lol
    Last edited: Dec 1, 2010
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  15. stu_m
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    stu_m Active Member VCDS Map User

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    [Dec 4, 2010]
    well after reading some of the replies i guess mine is just normal then!
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  16. defsix
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    defsix Member

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    [Dec 4, 2010]
    I can agree with the diesel engines. It takes a while for them to heat up in this weather and you will cool it more so running heaters on full.
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  17. Turkster
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    Turkster Bro.Paul 2.5TDI Quattro Sport

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    [Dec 5, 2010]
    dont forget the extra cold weather will blast your rad with extra cold air and cool the water/anti freeze more than normal, then when you add the heating being blasted at full pelt, its gonna make the temp drop a jar or 2,

    id just make a note of the temps right now and see if it continues when the weather temps rise and see if it all just vanishes,
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  18. iyrix
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    iyrix Member

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    [Jan 10, 2011]
    Hi Guys,

    Mine has started to act funny as well, im poping to Audi today to pick up a new thermostat and temp sensor. Hopefully i can get these fitted over the weekend.

    The temp on mine is certainly taking longer to get to 90c and when it gets there it drops of slightly at any time. Before it would just get there and sit.

    Do you think its possible when i had the water changed they used the wrong coolent?

    Thanks
    G.
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  19. simon.m
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    simon.m Active Member

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    [Jan 10, 2011]
    sounds like the temp sensor mate ;-)
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  20. iyrix
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    iyrix Member

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    [Jan 10, 2011]
    :) tuning my vagcom this weekend, GT5 took over weekend gone.. lol
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  21. iyrix
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    iyrix Member

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    [Jan 10, 2011]
    going to get a new thermostat and temp senor today.
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  22. simon.m
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    simon.m Active Member

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    [Jan 10, 2011]
    Gt5 that's on ps3 isn't it lol oh well can't play with both cars at once lol
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  23. iyrix
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    iyrix Member

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    [Jan 11, 2011]
    Just picked up these parts from Audi... ouch not cheap.

    Temp sensor about £15 and thermostat was about £30! foockers!
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