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2.5TDI Temp Gauge Problem

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by VagCabby, Jan 16, 2013.

  1. VagCabby
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    VagCabby Active Member

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    [Jan 16, 2013]
    Hello, My temp gauge in my A4 has been playing up for nearly 3 months now. First off it was hitting 90 degrees and then dropping all the way to 50 then to 90 then 70 then 90 and so on. I Put this down to the CTS being faulty so i changed that. After changing the CTS it still wasn't cured completely, it would raise to in between 70 and 90 but since this cold weather has come along its been sitting at 70 or just below 70. So i thought it was the thermostat being stuck open but one thing which is confusing me is that my heating is fine! I drive the car and after about 2 mins I have warm air coming though the blowers and after about 10 mins I have scorching hot air coming out the blowers! I tested the heat of the air coming out of the blowers with a cheap thermometer and it was showing the temp while being set to HI as 80 degreesor there abouts. I also tested the water in my header tank and that was around the 85 degree mark.....so could this just be a faulty CTS again and the new one I bought was dodgy? VCDS shows the temp the same as what my gauge shows but if i unplug the CTS that sits at the top of the engine VCDS shows the temp alot lower for example, when plugged in it was showing 68 degrees, when I unplugged the CTS it showed 38 degrees....are there 2 CTS's on the 2.5 TDI? if so where is the second one? VCDS shows no faults with the car.
    Last edited: Jan 16, 2013
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  3. Greeny233
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    Greeny233 Active Member

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    [Jan 16, 2013]
    For the price of a thermostat I'd try that next. I had the same problem with mine (heaters were still hot), changed the CTS first and no change, fitted new stat and it worked fine.
    After that if you still have a problem it could be the gauge.
    #2
  4. BlackQuat
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    BlackQuat Well-Known Member VCDS Map User

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    [Jan 16, 2013]
    Thermostat is a pain in the arse on the 2.5
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  5. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [Jan 16, 2013]
    Agreed, with new timing gear etc its typically £500.
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  6. VagCabby
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    VagCabby Active Member

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    [Jan 17, 2013]
    Yeah that's why I was hoping its not the thermostat due to it being a timing belt off job to change the damn thing! ,timing belt isn't due yet and in the middle of buying a house and getting married in April I didn't really want to have to Falk out for the timing belt just yet but I may have to :( l try a genuine CTS as the one I have is a cheapie and see how it goes! I very mechanicly minded, carried out engine conversions on my last 3 cars etc but I have never worked ion a v6 nor a diesel so abit weiry of doing the belts myself.
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  7. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [Jan 17, 2013]
    I'd definitely try a genuine CTS before doing anything else.
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  8. adamss24
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    adamss24 Well-Known Member

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    [Jan 17, 2013]
    I can change the thermostat for 100 + parts. You can get a cheap £6 part from Euro Car Parts or you can get a genuine audi one- about £28 including the seal... Based in N. London...
    Chris- 07789912128.
    #7
  9. Mike B
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    Mike B Member

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    [Jan 17, 2013]
    Cant see how it can be the stat if its warming up OK in this weather
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  10. VagCabby
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    VagCabby Active Member

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    [Jan 17, 2013]
    my thought exactly, going to try a new genuine CTS first before I think what to do next. Although don't diesels have some sort of electric heating which starts to heat your vents the moment the car is started to get the cabin warm in cold weather? I read it somewhere on the forum once.

    cheers for the offer Adam. I'll see how things go but I think if it is the thermostat ill just get the timing belt done for piece of mind!
    #9

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