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Thread: Temp Sensor Thread Size

  1. #1
    Super Moderator LarrBeard's Avatar
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    Temp Sensor Thread Size

    Is the thread for the temperature sensor 3/8 NPT?

    I know that there is an adapter for one of the heads, but I am asking about the basic sensor.
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    Super Moderator gmwillys's Avatar
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    I know my '46 has a 1/2" NPT, with a 3/4" NPT flush mount reducer. I have a Kaiser Supersonic head, so this may be the source of the discrepancy. I agree that yours is 3/8" NPT. Wrench size should be 1/2".

  3. #3
    Super Moderator LarrBeard's Avatar
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    Temp Sensor Thread SIze

    Quote Originally Posted by gmwillys View Post
    I know my '46 has a 1/2" NPT, with a 3/4" NPT flush mount reducer. I have a Kaiser Supersonic head, so this may be the source of the discrepancy. I agree that yours is 3/8" NPT. Wrench size should be 1/2".
    Thanks.

    I'm doing some fiddlin' with a gadget to use the modern sensors to drive the upside down gauges in the 46 - 49 trucks. I'm making a holding fixture to run resistance vs. temp curves; Pot of hot water and the wife's meat thermometer.

    Modern sensors drive the gauges backwards ... hot is 100-degrees and cold is 212.
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    Super Moderator gmwillys's Avatar
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    I found some information on King Seeley gauges/senders from the early Ford sight. It sounds to me that there are issues with the reproduction sending units. It is a common problem from the way it reads, and the gauges are interchangeable between the Ford and Willys gauge cluster, but both work opposite from one another.

    https://www.fordbarn.com/forum/showt...8308&showall=1

    Old 09-09-2017, 10:59 AM #21

    flatheadmurre

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    Default Re: Temp gauge works backwards


    From what you´re saying i suspect someone transplanted in a meter and sender that works the other way.
    Taking a meter from an early Jeep would be acting like this...and the face of the meter and needle fits to the jeep unit perfectly...only way to know for sure is to take the meter out and look.
    So that the faceplate and needle looks the same doesn´t mean the meter itself is the original.
    Last edited by gmwillys; 10-02-2018 at 12:45 PM.

  5. #5
    Super Moderator LarrBeard's Avatar
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    Thread Size

    Well, so much for our eyeball guesses.

    I went over to my local Fastenal and we looked through tap drawers until we found one that matched the threads on the sensor.

    They're 1/4-NPT; technically 1/4-18 NPT. Tap drill is 7/16".

  6. #6
    Super Moderator LarrBeard's Avatar
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    The original sensor was a thermostat/circuit breaker type of unit . Cold engine kept the switch closed, gauge internals heated up and moved the needle to the left. As engine warms, switch stays closed shorter period of time, gauge innards cool off, needle swings to the right.

    The post-'50 gauges use a variable resistance sensor, hotter goes lower resistance. When you tie this to the early gauges, you get the meter going bass-ackwards - and swapping the leads doesn't do anything.

    The answer is a "voltage controlled pulse width modulator" to mimic the on-off action of the original sensor. Maybe I can get something to match the gauge calibration .... or at keast center up in the middle and go the correct direction. Cold is left, hot is right - operating temp is in the middle!

  7. #7
    Super Moderator LarrBeard's Avatar
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    "From what you´re saying i suspect someone transplanted in a meter and sender that works the other way."

    I'm the on who did the transplant, way back about '72 or '73. I swapped an F-134 for the original L-134 (which had the correct sensor!) and by the time I figured out that sensors didn't swap out, the L-134 was long gone.

    Moral to the story - if you have an L-134 prior to '49 or '50, your sensor is rare and precious.

  8. #8
    Super Moderator gmwillys's Avatar
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    My eyes were way off. 1/4" NPT makes more sense. I'm sure my '46 is 3/8" but now will have to go out and check. So much for thinking. Thank you for the info.

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    Hello, I get fact that the gauge is backward. But there are a number of posts that state "...once you turn the key on the needle moves to the left." Mine does not move off of 212, so does that mean the temp meter is bad? I do have a 12 V system with a volt reducer, 12V to 6V, for all the gauges. I currently have a KS #9 sender and I get an ohm reading if I stick the sender in boiling water. As always any help is greatly appreciated. By the way you help me with my amp meter questions months ago and it work out just as you said it should. Should have asked then about the temperature meter and sender. Would still like to use my existing cluster but it is getting harder to justify. Tony

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    I found, but still monitoring it, a King Seeley # 9 temperature sender replacement. A Ford 1936 -1948 temp sender, 01A - 10990. It's been about two weeks and engine temp and KS gauge are tracking very well.

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