60' C-1 Temperature Gauge Erratic Reading - NCRS Discussion Boards

60' C-1 Temperature Gauge Erratic Reading

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  • Russell L.
    Frequent User
    • January 1, 2003
    • 43

    60' C-1 Temperature Gauge Erratic Reading

    My 60' has always ran cool and temperature gauge never read higher than 180 degrees even up mountainous areas. Had forward wire harness replaced and at same time changed Temperature Sender to a Corvette Central unit. Readings then went to 180 as before but increased while driving to 200 and 210. Strange thing was reading would change while driving from say 200 -210 back to 180 within 8-10 seconds so erratic. I used a infrared thermal temperature gun on the upper and lower radiator hose and found normal readings of 185 top and 170 lower. I then purchased an NOS temperature sender unit and installed which resulted in not change to these erratic readings. I changed the thermostat as well with another 160 degree unit and no change again. I then pulled the Dewitt high capacity radiator and had an old timer radiator shop pressure rinse and was told that it was fine and no sign of any blockage either. I also pulled my temp gauge and sent out for restoring and was told that it was fine so they sent it back to me with no work required. I might add that the radiator never overheated and car never gave any sign of actually running hot either.

    I have attempted to re-install the first temperature sender I removed but can no longer find it for some reason. I also might add that I had an issue with the wiring under dash that I was told that some wiring was not connected properly but that seemed to fix the emergency brake light from staying on even with brake lever was collapsed only.

    I have been told that there could there be some grounding issue going on here that would cause the temp to move around so much in the course of driving as it doesn't just go high and stay there it moves around within 8-10 seconds and could actually go lower when I encounter traffic which I might have to slow down for.

    I could use some advice on what to do next, I bought a resister that I could adjust the temp reading to be correct but as the temp fluctuates it is not just too high all the time.
  • Don H.
    Extremely Frequent Poster
    • December 1, 1981
    • 1487

    #2
    Re: 60' C-1 Temperature Gauge Erratic Reading

    Did you try to run a separate wire from the sending unit to the gauge?

    Comment

    • Russell L.
      Frequent User
      • January 1, 2003
      • 43

      #3
      Re: 60' C-1 Temperature Gauge Erratic Reading

      No I have not tried that if that work then of course it would mean the wire to the sending unit from the gauge is bad.

      Comment

      • Frank D.
        Expired
        • December 27, 2007
        • 2703

        #4
        Re: 60' C-1 Temperature Gauge Erratic Reading

        I had a similar issue on my 63; if your temp sending unit wire is the same the engine side terminal is a "slide on" type that goes on the nub at the top of the sender. Mine was actually quite loose and turned easily...

        I actually had to tighten that connector up to get a consistent reading.

        If you aren't using some sort of sealant on the sender threads there is almost no way it couldn't be well grounded and its easy enough to measure... The C1 gauges have small (1/4" ??) nuts on the back that secure the sender wires; you need to make sure those are tight with no issues.

        Playing with an external resistor will do nothing for this issue...but you could get a Wells-TU5 sender and install it just to eliminate that component; they are often inaccurate but a cheap way to do a "quick and dirty" test on the sender consistency...

        Comment

        • Edward B.
          Very Frequent User
          • January 1, 1988
          • 537

          #5
          Re: 60' C-1 Temperature Gauge Erratic Reading

          Rapid changes in readings are electrical in nature. Try a temporary by-pass wire as suggested by post #2.

          Comment

          • George J.
            Very Frequent User
            • March 1, 1999
            • 775

            #6
            Re: 60' C-1 Temperature Gauge Erratic Reading

            I recently had an issue with my '65, where the gauge was jumping around slightly. It was the connector on the thermostat. It must have had some corrosion. I moved it around a bit, and that solved it.

            Comment

            • Russell L.
              Frequent User
              • January 1, 2003
              • 43

              #7

              Comment

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