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  1. #1
    VXRed 82Matt's Avatar
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    10th December 2018
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    Default Aftermarket temp gauge puzzle

    My car came with an aftermarket gauge but it always over read. I didn't like it anyway so bought a new gauge which came with a new sensor. I cannot get it to read properly when the engine is on. As soon as you switch the engine off it reads what the hidden menu reads. I've tried both sensors. Different cables..even stood at the front of the car bonnet up with gauge powered and earth directly to the battery and still it overheads like crazy. Engine off and its bang on.

    Has anyone had similar issues and what was the solution? Thanks

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  2. #2
    VXR enough COSWORTH's Avatar
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    What make is the gauge you bought?
    Where did you buy it?
    Any pics of wiring loom from the new gauge and sensor

  3. #3
    VXRed 82Matt's Avatar
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    Oh both gauges are sub 20 quid Ebay specials. The wiring however has been changed and tested semi professionally and still no joy. I'm aware this points the blame towards the gauges but thought for both to be dud is maybe unlikely so posted this thread to see if anyone else has experienced the same. If no one has experienced this I'd be tempted to splash out but a bit reluctant as it stands.. if only because of how accurate they read once you shut the engine off

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  4. #4
    VXR enough COSWORTH's Avatar
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    What wiring is on the back of them ?

    Positive red should go to red under cig lighter with a switched live
    Earth should go to a bolt somewhere.
    Then there should be wires going to the sensor.
    Is it oil temp or water temp?
    What wires are there on gauge for live etc and what wires are there on sensor wires

    Without him this info no one can really help as its a bit vague

  5. #5
    VXR enough andrewt1971's Avatar
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    Is the sensor a single or two wire type?

  6. #6
    VXRed 82Matt's Avatar
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    Thanks lads. It's a simple 1 wire to the coolant sensor and the red wire was going to the ciggy lighter and earthed to an unknown location. Our tests we went straight to the battery since we wanted to hold the sensor wire away from the coil pack cables (we thought they might have been interfering)

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  7. #7
    VXR enough andrewt1971's Avatar
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    As a test take the earth from the gauge directly to the sensor body instead of the chassis or battery and see if that makes any difference.

  8. #8
    VXRed 82Matt's Avatar
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    Quote Originally Posted by andrewt1971 View Post
    As a test take the earth from the gauge directly to the sensor body instead of the chassis or battery and see if that makes any difference.
    Hmm I'll try that at the weekend thanks. Just out of interest what was your thought behind this test mate?

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  9. #9
    VXR enough andrewt1971's Avatar
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    Because the sensor is earthed via the engine and the gauge to some point on the chassis there is the potential for both 'earths' to be at a different level with respect to each other. This ground offset is possibly why the gauge reads correctly when the engine isn't running, there's less current flowing from things like the alternator which means the offset is less. If you put the 'earth's' together and the gauge reads correctly that's your problem. This is why you hardly ever find a single wire sensor on modern cars.

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