Electrical Temp gauge not reading correctly

Discussion in 'Classic Mustang Specific Tech' started by craig3x, Dec 11, 2012.


  1. craig3x

    craig3x New Member

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    the temp gauge on my '65 is reading hot, but I had a laser temp of the engine done and it's reading 178 degrees. Any ideas why it's reading incorrectly? Could it be an old brittle wire? Does resistance make it read hotter?
  2. bartl

    bartl Member

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    The opposite. The more resistance, the LOWER the gauge reads. Sounds like a bad sending unit.
  3. Jake2012

    Jake2012 Member

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    Agree with Bartl , I'm no autoelect but from experience most faulty temp gauge reads are caused by a faulty sender unit. Suggestion, not sure if you can test output of the temp sender unit ? If not, try changing the sender unit b4 doing other fault testing.
  4. tx65coupe

    tx65coupe Active Member

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    What about the fuel gauge? It could be the instrument cluster voltage regulator. I have an electronic solid state one now. The only mechanical one I have had that works close to right is the original one.
  5. 2+2GT

    2+2GT Well-Known Member

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    I agree. A couple years ago, I tested replacement senders from every manufacturer. Standard, Echlin, Delco, you name it. Ω was tested at 100°F. They all sucked, not even close. If you don't have an original Autolite or Motorcraft replacement, get one. They aren't available new, so you'll have to find one.
  6. bartl

    bartl Member

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    The only other option is to find a resistor with the proper value to "calibrate" the gauge.
  7. craig3x

    craig3x New Member

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    hmmm, I bought the car a few months ago, and it has a new intake on it and the sender looks to be new as well. My fuel gauge is accurate as far as I can tell, so I don't think its a cluster problem. Not sure what to do if all the aftermarket senders are crap as 2+2GT says

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