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Thread: Weird Temp. Gauge Issue

  1. #1
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    Default Weird Temp. Gauge Issue

    OK< background:

    Noble M12, originally 2.5. I've installed a 3000 mile M400 rear clip - engine, gearbox, turbos, ECU. Everything.

    All up and running, but my water temp gauge reads exactly double.

    Using the diagnostic software, i can see the ECU is reading the temp. correctly. The thermostat opens, the fans switch on, the fans switch off correctly.

    But the gauge reads double!!!

    I have checked my wiring from the white loom plug to the gauge - perfect.

    The 12V+ve and earth to the gauge is correct.

    I have confirmed with the factory that there is only one version of the temp gauge.

    Ideas anyone????

  2. #2
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    Just throwing some ideas out......Are there any little switches on the back of the guage that may just need to be set properly? Loose connection in the white loom plug? Are you using the M400 wiring loom that is somehow different than the 2.5 loom? Is the 2.5 temp gauge somehow different than an M400 gauge (resister missing or something?) Could it just be that the gauge has gone bad?
    Last edited by caccobra; 06-28-2010 at 04:10 AM.

  3. #3
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    Thanks for your reply.

    Quote Originally Posted by caccobra View Post
    Are there any little switches on the back of the guage that may just need to be set properly?
    No switches on the temp guage.

    Quote Originally Posted by caccobra View Post
    Loose connection in the white loom plug?missing or something?)
    New plug and terminals, profesionally crimped.

    Quote Originally Posted by caccobra View Post
    Are you using the M400 wiring loom that is somehow different than the 2.5 loom?
    M400 engine loom. I have run new wires from the white plug to the temp gauge and fan relays. These are the only wiring differences.

    Quote Originally Posted by caccobra View Post
    Is the 2.5 temp gauge somehow different than an M400 gauge (resister missing or something?)
    The factory have confirmed there is only one temp gauge for all models - no varuiations, no updates.

    There could be a resistor somewhere in the loom, but no one is aware of such a thing.


    Quote Originally Posted by caccobra View Post
    Could it just be that the gauge has gone bad?
    Have tried a second gauge from a 3R, same result.

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    Celsius versus fahrenheit?

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    Quote Originally Posted by pma1010 View Post
    Celsius versus fahrenheit?
    Hey! Never thought of that!

    But just done another check - gauge is showing exactly double whatever the ECU diagnostics is displayng.

    (C to F would be double + 30).

  6. #6
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    maybe the signal is generated by the ecu
    do you have the new ecu?
    I'll check the outputs and confirm they are the same
    -Troy Fralick
    troy@nobleupgrades.com
    Tallahassee Speed Shop, Inc.
    5338 Gateway Drive
    Tallahassee, Fl 32303
    850-597-8919
    904-838-9150 cell
    And
    Remade by Hand, Inc.
    Porsche Restorations
    173 McCallister Rd
    Crawfordville, FL 32327

  7. #7
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    Quote Originally Posted by NobleTech View Post
    maybe the signal is generated by the ecu
    do you have the new ecu?
    I'll check the outputs and confirm they are the same
    Trevor at Roush (our guru mapper in the UK) has confirmed the ECU does generate the signal to the temp gauge.

    He also confirmed with iginition on, and temp sensor unplugged, temp gauge should read 60 degrees, the default temp outputted by ECU.

    I've done that test and mine reads 120 degrees!

    Would be good to know wht your gauge voltage is if you do the above test.... Both at the white plug (unplugged) and the gauge. This would confirm if there is an undocumented resistor in the body loom...

    The wholre M400 rear clip i bought was a verified 3000 miles, and has the correct MBE ECU. Obviuoly i'm assuming the gauge was reading correctly in the previous car. Since i know my wiring is correct, and there is only one gauge for all Nobles, that's why i'm wondering whether there is a resistor in the circuit somewhere.
    Last edited by peterguk; 06-28-2010 at 02:24 PM.

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