Temperature sending unit problem.

Slant 6 Engines

  1. 68_Valiant_Wilson

    68_Valiant_Wilson Active Member

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    The temperature sending unit on my Valiant does not seem to be working. I have replaced it twice and it hasn’t worked either time. I have tested the temperature sending wire and the gauge and both appear to work fine. I ground the temperature sending wire on the alternator and the gauge will jump up to hot but fairly slowly. And once I take it off of the ground it falls slowly back down to cold and then goes below cold and sometimes points below the dash. When I have it connected to the temperature sending unit it just sits below or at cold. I’m not real sure what this could be. Any advice is appreciated.
     
  2. Capt46

    Capt46 FABO Gold Member FABO Gold Member

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    Does your gas gauge work?
     
  3. 68_Valiant_Wilson

    68_Valiant_Wilson Active Member

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    Yes
     
  4. Capt46

    Capt46 FABO Gold Member FABO Gold Member

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    6 or 8 cyl
     
  5. 68_Valiant_Wilson

    68_Valiant_Wilson Active Member

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    Slant 6 3.7 liter
     
  6. Capt46

    Capt46 FABO Gold Member FABO Gold Member

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    early sender with later gauge or a later sender with early gauge makes the gauge read improperly.
    Make sure you have the correct ohms.... someone here with give better information that work with the information you provided. Sit back your help is on the way...
     
  7. 68_Valiant_Wilson

    68_Valiant_Wilson Active Member

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    Thanks! Really appreciate that!
     
  8. slantsixdan

    slantsixdan =..=

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    1. Does the fuel gauge work normally, or is it slow/defective, too?

    2. Make sure you are using the correct sender. There are many that fit and hook up, but have different resistance curves. Try a Standard Motor Products № TS-17.
     
  9. 68_Valiant_Wilson

    68_Valiant_Wilson Active Member

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    I haven’t noticed the fuel gauge being slower than usual. I’ve already bought two senders I couldn’t tell either one worked but would the kind of resistance curve be in the manual? I’m kind of sick of buying them and i certainly don’t want to buy anymore if they won’t work.
     
  10. halifaxhops

    halifaxhops It's going to get stupid around here! FABO Gold Member

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    Low is 87 high is 27 I believe.
     
  11. slantsixdan

    slantsixdan =..=

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    How about its accuracy? Does it accuratel show you 1/4 tank, 1/2 tank, 3/4 tank, and a full tank? Even though the question is about the fuel gauge, this is important to diagnose the problem you're having with the temp gauge.

    Which ones, exactly? Brand and part number.

    Unfortunately not. The manufacturer's publication says 15–19 ohms at 220°F, which doesn't help much. I've pinged my engineering guy at SMP and I hope to hear back from him next week.
     
  12. RedFish

    RedFish Well-Known Member

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    Description reads like a faulty gauge to me. I might have considered a loose contact nut behind this gauge but... "sometimes points below the dash". At off the needle should go to the same home position every time. Sometimes it stops at the C and other times well below the C ? Bad gauge.
    The same ohms range and same tester applies to all these gauges and senders. 80 ohms is no needle movement. 73 ohms is visible movement to a low position ( like the first has mark ). 23 ohms is near the center of the range/screen. 10 ohms is the high end of the range.
    Shorting the sender wire to ground is zero ohms. That can generate heat and movement that normal within 80 to 10 range cannot.
     
  13. Dana67Dart

    Dana67Dart The parts you don't add don't cause you no trouble FABO Gold Member

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    You can determin the curve of the sender. Fill a sauce pan with room temp water. Suspend the sensor in the water. Attach an ohm meter to the body and the center post. Be sure the center post and lead dont get in the water. Now turn on the stove and take water temp and ohm readings every 10 deg till the water boils. Plot in excel and there you have it the curve of the sender.
     
  14. Dana67Dart

    Dana67Dart The parts you don't add don't cause you no trouble FABO Gold Member

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    My bet is a bad temp gauge since it is going below normal low
     
  15. 68_Valiant_Wilson

    68_Valiant_Wilson Active Member

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    That was probably not the best description on my part. The only time the gauge sits below C is after I’ve taken the sending wire off of ground. It always sits at C and then I’ll connect it to ground and it will move to H but once I take it off of ground it usually reads well below C. Eventually it slowly moves back to just sitting at C again.
     
  16. slantsixdan

    slantsixdan =..=

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    Yes, but that won't do much good unless/until we can get the maker to cough up what the curve should be.
     
  17. 68_Valiant_Wilson

    68_Valiant_Wilson Active Member

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    1)The gas gauge works fine. I’ve never had any problems with it. I’ve never run out of gas at least haha.
    2) When I say I bought two, I meant that I went to autozone and just got what they said would fit and hoped for the best. When it didn’t work I figured maybe the sending unit was a dud so I got it replaced and the replacement doesn’t work either. I don’t have the information on brand and part number. I was looking around and managed to find the original sending unit that was in it when it worked. Unfortunately I can’t find any kind of part number on it.
     
  18. 68_Valiant_Wilson

    68_Valiant_Wilson Active Member

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    I meant to also say I’m going to call autozone tomorrow and try to get all the information I can about the unit I have
     
  19. Dana67Dart

    Dana67Dart The parts you don't add don't cause you no trouble FABO Gold Member

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    upload_2018-2-23_21-1-17.png

    Here is a curve for an Airtex 1T1010 and the gauge in my 1967 Dodge Dart

    For what ever its worth
     
  20. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    You are wasting your time. Modern parts people barely know how to look up application, most of 'em anyhow. Even back in my day, the catalogs did not show resistor / temp curves for the thermistors.

    Get some resistors as Redfish eluded to above and test the gauge "system." Same resistors can check fuel, and if you have it, oil. Here:

    c-3826-jpg.jpg

    That will tell you whether the gauge/ wiring/ IVR as a system is halfway accurate
     
  21. slantsixdan

    slantsixdan =..=

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    Could easily be some or all of the problem. Poor-quality parts = car that doesn't work well.
     
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    • slantsixdan

      slantsixdan =..=

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      Also, I had one of those awake-at-3am thoughts about this: you don't happen to have used Teflon tape or thread sealant or anything else on the sender(s) you installed, did you? That needs to be a clean metal-to-metal junction because current has to flow.
       
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      • RedFish

        RedFish Well-Known Member

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        You could do some testing with a ohms meter. Check the senders base to neg' battery terminal. You're looking for near zero resistance. As stated above, a lot of thread tape can effect this path. Most new senders have a painted coat of red colored sealant on the threads. That should be all it needs.
        Start the engine and let it warm up. When the 180 degree thermostat opens the sender contact post to neg' battery terminal should be somewhere near 34 ohms. If that checks good, hook up the sender wire. Gauge needle should climb to low end of normal range.
        Have you considered thermostat stuck open?
         
      • 68_Valiant_Wilson

        68_Valiant_Wilson Active Member

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        The original unit that was in it when it worked does look like it had some kind of sealant but there isn’t anything like that on the new units I got. This is what to original unit looks like

        image.jpg
        The new units are just bare metal contact. I actually see two points where it looks like sealant was put on. The obvious red looking tape and also the gray area above the threads.
         
        Last edited: Feb 24, 2018
      • 67Dart273

        67Dart273 FABO Gold Member FABO Gold Member

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        NEVER EVER have I seen a problem with a sender installed with sealer. IF YOU SUSPECT THIS simply take your ohmeter set to "low ohms" and "stab" one probe into the brass of the sender ground, and stab the other into a good block ground. Be sure to poke hard through the paint.
         
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