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Engine temperature reduces LOADS with air con...

Discussion in 'A3/S3 Forum (8L Chassis)' started by nick4501, Nov 7, 2010.

  1. nick4501
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    nick4501 Member

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    [Nov 7, 2010]
    Hi guys.

    Hopefully just a quick one... I've noticed that as soon as I put the aircon on, my engine temperature drops very quickly and eventually ends up on the initial position / 60. I'm so concerned that I'm driving my car too hard whilst cold, that I actually turn the aircon off (making the windows steam up!), so that it can get up to temperature, so I don't feel bad for putting the hammer down...

    Surely this isn't normal? It normally takes about 10 mins of driving for the needle to even start moving (with the aircon off), so I've been wondering if the stat is on it's way out anyway...could this be the cause?
    #1
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  3. BASS 666
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    BASS 666 BMW aye right dead on..

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    [Nov 7, 2010]
    stat or coolant temp sensor.
    #2
  4. pj123
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    pj123 Member

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    [Nov 7, 2010]
    You need to replace your thermostat.Temperature should sit bang on 90 degrees at all times. Sounds like your dial is reading correctly so prob not the coolant temperature sensor. If you do it yourself just remember to disconnect the battery as you will be working near the live terminal to the alternator and could touch a spanner onto it.
    #3
  5. luke2702
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    luke2702 Member

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    [Nov 7, 2010]
    Just done mine again today (2nd in 7 months) make sure you buy a new dipstick guide as mine broke again this time. Didnt disconnect battery as cant get a spanner in there to work had to use allen keys. Bloody pain it is!!!
    #4
  6. pj123
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    pj123 Member

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    [Nov 7, 2010]
    Any idea why you needed to do it again so soon?

    Abtech in Southampton did mine years ago, shorted onto that connection, denied it and then tried to charge me to fix it when my battery went flat a week later. Would not recommend this garage and have done everything myself ever since! At least if I'm going to cock it up i only have myself to blame! Bet they gave it to the trainee. Anyone reading this that uses Abtech, use Monks in Chilworth instead!
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  7. luke2702
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    luke2702 Member

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    [Nov 7, 2010]
    When i removed the faulty one this time, i found that the pin which is used as a guide for the main body, had come out of its guide slid across and was holding the stat in the open position. Note this was cheap one of ebay bought the new one from GSF looks better and has a part no stamped on it....
    #6
  8. nick4501
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    nick4501 Member

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    [Nov 7, 2010]
    Thanks for the info guys.

    I replaced my temp sensor about 4 months ago, so I would have thought that is fine. How can a dodgy stat result in the engine temperature dramatically reducing when you turn the air con on?!

    Will I need to drain the coolant to do this?
    #7
  9. PaulTheo
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    PaulTheo Member

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    [Nov 7, 2010]
    I had this on a previous A4 where if I used the AC or when cruising on the moterway (80 ish) the faster I went the cooler the engine!!! and I replaced the thermostat and it did not make any difference which really confused me. I was begining to think VAG-COM was lying to me but as I had access to some data loggers I attached a couple temp recorders around the coolant system and it confirmed that the temp did drop. I them bought another genuine one from Audi and it was perfect again never moved from 90 just as it always used to be. I had tested the previous thermostats and they appeared to work perfectly?
    #8
  10. finesse
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    finesse Active Member VCDS Map User

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    [Nov 7, 2010]
    had the same issue, changed thermostat, problems gone
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  11. PaulTheo
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    PaulTheo Member

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    [Nov 7, 2010]
    The fan for the condenser is cooling your radiator and the thermostat is not regulating the coolant flow.

    You will need to drain the coolant and make sure you bleed the system when you fill it back up.
    #10

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