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Thread: TDI Low/no tempoerature readings. Two A2s with the same issue

  1. #1
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    TDI Low/no tempoerature readings. Two A2s with the same issue

    Two of the cars I have bought recently (both TDIs) suffered from pretty much identical problems and it wasn't quite what I expected.

    Both had temperature gauges that hardly moved off the 60 degree mark.
    So I immediately thought it would just be a broken temperature sender.

    I replaced the sensor on the first one and it made little difference so I jumped to a conclusion that the new tempo sensor was faulty (that happens more often than you would think), but no, even after another sensor change the problem persisted.

    So there was only one culprit left, the thermostat. I must admit that I didn't think it could be that because if the temperature sender was working correctly it means that the engine was running at 60 degrees or less, even at motorway speeds (I know these TDIs don't give off a lot of heat, but not getting above 60 degrees, even under load???

    I carried out one final test, I did the same run, but this time leaving the climate switched off (the theory was that with the climate on the electric fan runs regardless of engine temperature, so switching it off should see an increase in temperature. Sure enough the needle did start to rise and it hit 75 degrees.
    To me that proves that the temp sender had NOT died completely at least.

    So it did seem to point to a thermostat problem, so that was changed.

    FIXED !!! The temperature rose to 90 (where it should be) quite quickly and stayed there, as it should !!!!

    A few days later the other TDI (which I thought had a temp sender issue too) acted the same on a run with the climate switched off, the temp rose a little.

    So today the thermostat was changed on that one and hey presto, a perfect temperature of 90 quickly showed and stayed there.

    So if you have a TDI that is acting like the sender has failed, try the same check, switch off the climate and see if the temp rises. If it does, you have a failed thermostat. They are reasonably cheap and pretty easy to replace on the TDI AMF engine at least. They are in the front and the alternator mounting is slightly in the way, but it is a DIY job.

    I hope this helps if you have similar issues.

    Steve B

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  3. #2
    Join Date
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    Had the same issue on my 1.4i, same answer although in my case it was also a missing rubber gasket as 2 were given but i had 1 installed as the other was deemed a spare, nope both are required. Easy fix but took a while.

  4. #3
    That's interesting. I have the same issue on my TDI. Temperature sender was replaced during a cam belt change but it still reads low.
    Is replacing the thermostat a job I need to do now? Will it cause problems if I leave it for a month or so?

  5. #4
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    Quote Originally Posted by sunsurfer View Post
    That's interesting. I have the same issue on my TDI. Temperature sender was replaced during a cam belt change but it still reads low.
    Is replacing the thermostat a job I need to do now? Will it cause problems if I leave it for a month or so?
    If the car is running OK then you could wait a while, especially since the weather is warming up (a little)

    I wouldn't leave it much longer than 4 weeks though. The thermostat is on the front of the engine and it is a pretty basic one too, so the cost should be low.

    Steve B

  6. #5
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    Had exactly the same problem about 6 months ago, it was due a cambelt change anyway so i asked them to change the Thermostat whilst they were there.

  7. #6
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    Sep 2008
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    Greymouth, New Zealand
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    Thanks Steve - got the same problem with ours. Tried turning the aircon off (for several minutes) but the gauge still showed just over 60 degrees so it should be just the sender.

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  9. #7
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    Quote Originally Posted by trevorswaine View Post
    Thanks Steve - got the same problem with ours. Tried turning the aircon off (for several minutes) but the gauge still showed just over 60 degrees so it should be just the sender.
    The increase in temperature is not quick, I was doing motorway miles and after about 5 miles it started to creep up.

    The TDIs run surprisingly cool and so temperature changes take time.

    So before you spend on a sender try a longer run and even a small increase in temperature might indicate a thermostat issue.

    Steve B

  10. #8
    Stupid question but how do you turn the aircon on & off? Mine didn't come with a manual

    Sent from my ONEPLUS A3003 using Tapatalk

  11. #9
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    You can turn it off and on by pressing the "ECON" button Craig... if the orange or red light is illuminated on that button then the air con is "OFF" or running on an increased economy mode. If the orange light is off then its running at its full capacity, ie "ON", and should be super cool with a "lo" temperature setting.
    Last edited by Special edition; 18-05-2017 at 07:19 PM.

  12. #10
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    Quote Originally Posted by Craig View Post
    Stupid question but how do you turn the aircon on & off? Mine didn't come with a manual

    Sent from my ONEPLUS A3003 using Tapatalk
    Pressing the "off" button at the bottom of the climate panel is the best way for this test.

    By using that you are also not cooling the water down by blowing heat through the heater matrix.

    You are aiming to conserve as much heat in the engine as you can to try to get the temperature up high enough to register on the temp gauge.

    Steve B

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    Special edition (18-05-2017)

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