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  • Temp gauge question

    A year or so ago I replaced the temp and fuel gauges along with the sending unit in the tank. The sending unit needs adjusting as the fuel gauge reads low. I've just been too lazy to do it yet.

    My question is whether or not this would also cause the temp gauge to read low as I know the two gauges are connected somewhat. I've also replaced the temp sending unit. I'm running a 180 degree thermostat and it barely gets to the green line. Normally I wouldn't complain but the old gauge (back when it worked) read about in the middle with the same thermostat.

    Engine is a 304 in a 76 CJ-5.

  • #2
    Hello...

    Welcome to the board, fellow South Carolinian...

    No, it won't read lower because the gas gauge does. I noticed there is some difference in the calibration of the newer temp gauges versus the older gauges. (I actually wound up putting my old gauge back in.) You might try changing the temp sensor. That may or may not change the reading a tad. The gauge 'should' run near the middle at normal running temp. If you want a 'feel good' indication stick yourself a quality mechanical gauge in.

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    • #3
      Thanks. After driving it for 15 years with it reading one way it is rather disconcerting to have it read different now.

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      • #4
        Well.....it could,
        The Thermo gauge might read wrong if the regulator in the fuel gauge is off. Then both the temp and the fuel gauge will be off.

        Check the resistance on the temp sensor.
        It should be something like this:
        73 ohms Cold - Test when engine is slightly warm. A stone cold engine will read 400 ohms
        36 ohms Beginning of Band
        13 ohms End of Band
        9 ohms Hot

        You could buy a resistor to check your temp gauge before you spend money on a new sending unit.

        The fuel level sending unit should read like this:
        Empty = 73 ohms
        1/2 Tank = 23 ohms
        Full tank = 10 ohms

        A 25 ohm resistor from Radio Shack should put either gauge somewere in the middle of the band. If it doesn't then look into adjusting the gauge.

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        • #5
          Quite true...

          As usual, John is correct, CJ5, and his comment on the voltage regulation made me remember something.

          Let me explain further on why I wound up putting my old cluster back in. I installed a brand new cluster from Crown in Myrtle. The CVR was failing in the fuel gauge. Or at least, I'm pretty sure it was. I noticed every so often both gauges would go 'bonkers' on me. Eventually, each failed. This almost had to be the CVR going bad then failing altogether. But initially, while each was working properly, the new temp gauge didn't read as high as the old one and my gas gauge was accurate.

          However, John has a VERY good point with regard to the measurements. Using them will keep you from dropping the tank unnecessarily if you have voltage regulator trouble from the fuel gauge. (I was 'assuming' you hadn't properly calibrated your sending unit when you replaced it.)

          I might also add that the 'quality' of the new gauges available for the old CJs leaves a bit to be desired. Myrtle's orginal '77 gauges are still kickin'. The new gauges didn't last three months. And remember that you're 'supposed' to change them as a set if you have to replace them...again.

          p.s. John, would you post up with your link for him again? I believe it explains the CVR regulation in detail doesn't it?

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          • #6
            Shure, here are some Links.:

            Quick Reference for CJ Gauges.

            Quick test for CJ Gauges

            A little more in depth Troubleshooting guide

            Boring theory on how they are suppose to work

            Adjusting the CJ Gauges for the real nitpickers

            My Latest at Off-road.com

            Use this last one. I think I have every thing in here but it's the first time I had to deal with an "Live Human Editor" cutting things out to make room.
            Last edited by John Strenk; 03-15-2006, 11:36 AM.

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