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Coolant temp sensor wiring diagram and expected results

Jedan71 May 13, 2018

  1. Jedan71

    Jedan71 New Member

    How all, I am gong crazy trying to diagnosis my fault of no movement of my temperature gauge. I have 99 A4 avant 2.4 v6 Quattro. AGA engine code, the idle is erratic and bounces around 600-640. I have replaced cts sensor 3 times to same effect, aircon button tips (51) says 90 when running around and warmed up.
    I understand the cts works reversed high resistance at cold and no resistance at hot, so if I was too probe the sensor what values should I effect of which wire, which wires go to gauge abs which to ecu? I can't this info anywhere or people are holding out.

    Please can someone help, as parts and true knowledge is hard to get here in NZ.

    Thanx Alex

    Sent from my ONEPLUS A3010 using Tapatalk
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  3. aragorn

    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

    51 is not the correct readout, that one always shows 90. You need to use 49 to see the actual temperature.

    Use VCDS to view the coolant temperature within the ECU and also within the instrument cluster directly.

    Potentially a thermostat thats stuck open stopping the engine from warming up.

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