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TDi temp gauge

Discussion in 'A3/S3 Forum (8L Chassis)' started by mayurw, Sep 15, 2007.

  1. mayurw
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    mayurw New Member

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    [Sep 15, 2007]
    I have been having a problem with temp gauge for about 2 weeks and from reading some of the posts on this forum, I have so far replaced the temp sensor and the thermostat but its still not working 100%. The problem started when the gauge failed to move and I had been driving on the motorway for about 1hr. As I kept an eye on it I did notice it "float" between 60 and 90, it would normally stick at 90. Since the problem began I did notice 1 strange think, the pipe coming from the rad to the themostat housing was always cooler than the top hose which was coming from the engine. This is normal as the thermostat would only open once the car had reached a certain temp. I also checked the sensor readings via the cilmate control system and reading 49 would always reach a max of 30oC and 51 would be max 75oC.

    Today I wanted to check if the rad fans were operating so after driving for about 20mins I left the car running and monitored the pipes and readings. Checked the pipe to the thermo housing and it was considerbly cooler than the top one, 49 was still sitting at 30oC and 51 at 75oC. After about 20mins the housing pipe started to get hotter and as it did the 49 reading started raising and then stopped at around 96oC when the fan kicked in and started dropping.

    Now my question is that could I have a block in the rad ? which sensor is responsible for the 49 reading ? could I have an air lock ? where does the gauge on that dash get its reading from ?

    Another stange thing I've noticed is sometimes when I turn on the ignition, the temp gauge jumps over and above the max reading and then comes back down to 90 then slowly to 60, not sure if thats normal or not.

    I hope you guys can help me out.

    Thanks
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  3. mayurw
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    mayurw New Member

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    [Sep 16, 2007]
    update to the problem .....

    Last night I happened to be stuck in some heavy traffic and I was worried that the car might overheat so what I did was squeeze the pipe going into the thermo housing as it was warm and for some reason, this got the gauge working, the 49 reading went up to 90+ from 30 and even the fan kicked in. Now when I was checking the fans in my previous post, I do recall squeezing the pipes but at the time didn't think anything of it. Also on the way back home I did the same and again the gauge started working and so did the fans.

    What does this mean ?
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  4. Tooks
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    Tooks Active Member

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    [Sep 17, 2007]
    Sounds like you could have an air lock from what you describe?

    It's pretty easy to bleed the cooling system though, it pretty much does it itself.

    Also, I wouldn't discount the fact that your new thermostat might be faulty. Where was it from? It wouldn't be the first time that I've fitted a new part that turned out to be buggered...
    #3
  5. sprout99
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    sprout99 Member

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    [Sep 17, 2007]
    if temp gauge isn't rising but heating is ok - temp sender
    if temp is not rising and no hot air in car either thermostat is knackered or air lock. both would give same fault ans symptoms.
    #4
  6. mayurw
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    mayurw New Member

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    [Sep 17, 2007]
    the thermostat and the sensor were both brought from Audi. After changing both parts, the symptons are the same so changing them has made no difference. Heating is fine and has always been. Could I have a faulty sensor ? as I understand it, mine is a 4 pin so its 2 sensors, one to provide reading to the ECU and the other to the dash gauge.
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  7. sprout99
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    sprout99 Member

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    [Sep 17, 2007]
    :think:
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  8. grathies
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    grathies More Points Than Portsmouth FC

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    [Sep 17, 2007]
    Could be the actual cluster unit, seen similar before with fuel readings jumping about erratically
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  9. mayurw
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    mayurw New Member

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    [Sep 18, 2007]
    what if I just remove the thermostat for a little while ? would it be safe to drive it like that ?
    #8
  10. grathies
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    grathies More Points Than Portsmouth FC

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    [Sep 18, 2007]
    Youll find that the car will take ages to warm up, as your just letting everything thru, would be like the thermostat was jammed open
    #9
  11. mayurw
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    mayurw New Member

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    [Sep 22, 2007]
    had a vw tech have a look yesterday and the thermostat wasn't fitted properly, apparantly it "locks" into position, I knew it had to be fitted vertically but it also somehow locks by turning it into postion. So now all the pipes are getting hot so that's sorted but I still have the gauge problem and I don't think the fans are working. The fans did come on when I accidently turned the AC on, it that normal ? the car had been running for around 45mins. I checked the old temp switch yesterday with a multimeter and some wires attached to the switch, both sensors as I have a 4 wire switch seemed to be working as the resistance dropped as I put it into hot water. I need to understand where the 49 reading from the CC panel comes from as that is still stuck at 30oC and when the gauge does work, that raises to 90oC+. I'm just worried that I might overheat the car now and blow the headgasket :(
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  12. mayurw
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    mayurw New Member

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    [Sep 22, 2007]
    anybody know what the sensor/switch that is fitted to the rad ? its located under the battery on the right hand side
    #11
  13. mayurw
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    mayurw New Member

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    [Oct 3, 2007]
    It seems that my problem is an electrical one. A friend of mine has a vag-com and using this to check the sensor reading, the reading fluctuates between 30 and 130oC, this would explain why the reading via the CC unit only reads 30oC most times. Going to get the wiring checked out so I'll let you know how it goes......
    #12
  14. mayurw
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    mayurw New Member

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    [Dec 4, 2007]
    now I being told its the dash that's faulty .......... has anybody else seen this ? what did you to fix it ?
    #13

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