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  1. #1
    Join Date
    Sep 2017
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    59

    LS3 Coolant Temp Sensors

    My LA3 has two temp sensor locations, one on the driver side for the computer and one on the passenger side for your gauge. I bought speedhut gauges that come with a temp sensor fitting into an 1/2" NPT adapter (two pieces on the left). These are very standard fittings when installing the sensor in the manifold. The fitting on the left is what threads into the head which is 1/8" NPT. The diameter of the sensor does not fit into the adapter for the LS3. I see three options;

    1. Drill out the adapter to allow the sensor to fit.
    2. Machine the sensor diameter to fit the adapter.
    3. Drill out the head to allow the 1/2" NPT fitting to fit and use the speedhut sensor.

    i can tell you that option 1 does not work as I snapped the fitting off inside the head. Good news is I have some easy outs that worked like a charm with no damage to the head or threads.

    The ohm rating for the speedhut gauge is 240-33 ohms (140F-280F), which is specific to their gauges just like Autometer has different ohm rating for theirs.

    Has as anyone else run across this issue and how did you resolve it. OR, is there a better idea. I'm all ears. Thanks in advance.

    perry
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  2. #2
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    Apr 2010
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    Cove, Texas
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    I did. Drill out the adapter, screw the sender into it, then screw the whole thing into the head. I snapped the first one off just like you did until I figured it out. It makes it stronger as a unit.

    Since then, I have moved my temp sender to the upper hose. I was getting readings 20-30 degrees higher back there....

    T,

  3. #3
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    Dec 2008
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    Quote Originally Posted by TomMLS1 View Post
    I did. Drill out the adapter, screw the sender into it, then screw the whole thing into the head. I snapped the first one off just like you did until I figured it out. It makes it stronger as a unit.

    Since then, I have moved my temp sender to the upper hose. I was getting readings 20-30 degrees higher back there....

    T,
    I am having the same issue with mine now. I lost the original sender and I think the replacement has the wrong resistance, my temps are higher on my gauge than my handheld.
    Big dreams, small pockets....

    Chris--
    '72 Cutlass S LS2/T56 Magnum
    Bowler Performance, Rushforth Wheels, SC&C, ATS, Street Rod Designs, Speedhut, KORE3, Ridetech

    Project Motor City Madness

  4. #4
    Join Date
    Sep 2017
    Posts
    59
    Wow, this is a problem. Iv'e been working with Speedhut and unfortunately they have nothing that will work. They say their sensor will fit the 1/8" NPT adapter but not the M12x1.5 that perfectly threads into the head. I did talk with our local speed shop and they suggest moving it to the upper rad hose as well. Looks like I'm going shopping. Thanks for help.

    Perry

  5. #5
    Join Date
    Sep 2017
    Posts
    59
    Something else I'm strongly considering doing. I have dual rad fans. The power center for the LS3 looks after the rad fan and fuel pump. I want to install one fan connected to the PCM and have the other controlled almost as a backup using a Painless model (www.painlessperformance.com/wc/30104). Set it for 5-10F high than the computer controlled fan.

    Perry

  6. #6
    Join Date
    Apr 2010
    Location
    Cove, Texas
    Posts
    57
    Country Flag: United States
    I also have an LS3 with dual fans. Look at the Dakota Digital controller. A little bit more but it has much more capability. You can control both fans off and on temps, off at a certain MPH, fan cool down on key off and also has AC request capability....have to buy another relay, but mine works without a hitch.

    Even has Blue tooth now....

    https://www.dakotadigital.com/index....od/prd1207.htm

    T,

  7. #7
    Join Date
    Dec 2008
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    Detroit
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    Quote Originally Posted by Zombie666 View Post
    My LA3 has two temp sensor locations, one on the driver side for the computer and one on the passenger side for your gauge. I bought speedhut gauges that come with a temp sensor fitting into an 1/2" NPT adapter (two pieces on the left). These are very standard fittings when installing the sensor in the manifold. The fitting on the left is what threads into the head which is 1/8" NPT. The diameter of the sensor does not fit into the adapter for the LS3. I see three options;

    1. Drill out the adapter to allow the sensor to fit.
    2. Machine the sensor diameter to fit the adapter.
    3. Drill out the head to allow the 1/2" NPT fitting to fit and use the speedhut sensor.

    i can tell you that option 1 does not work as I snapped the fitting off inside the head. Good news is I have some easy outs that worked like a charm with no damage to the head or threads.



    The ohm rating for the speedhut gauge is 240-33 ohms (140F-280F), which is specific to their gauges just like Autometer has different ohm rating for theirs.

    Has as anyone else run across this issue and how did you resolve it. OR, is there a better idea. I'm all ears. Thanks in advance.

    perry
    Perry,

    I only see one sender on their site like yours and its 1/8npt thread correct? Are you saying that the sender will not fit all the way through the for the m12x1.5 to 1/8npt adapter fitting?
    Big dreams, small pockets....

    Chris--
    '72 Cutlass S LS2/T56 Magnum
    Bowler Performance, Rushforth Wheels, SC&C, ATS, Street Rod Designs, Speedhut, KORE3, Ridetech

    Project Motor City Madness


  8. #8
    Join Date
    Sep 2017
    Posts
    59
    Chris,
    That's right. The M12x1.5 adapter is what threads into the head and the sensor is supposed to thread into the adapter. The adapter is metric to suit the metric LS3. The bore diameter is smaller than the O.D. Of the sensor. I have since gone with an in line sensor in the upper rad hose. Turned out perfect and all wired up. Now to go look at the Dakota Digital dual fan controller. Ahhh, more money to spend.

    Perry

  9. #9
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    Dec 2008
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    Detroit
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    Quote Originally Posted by Zombie666 View Post
    Chris,
    That's right. The M12x1.5 adapter is what threads into the head and the sensor is supposed to thread into the adapter. The adapter is metric to suit the metric LS3. The bore diameter is smaller than the O.D. Of the sensor. I have since gone with an in line sensor in the upper rad hose. Turned out perfect and all wired up. Now to go look at the Dakota Digital dual fan controller. Ahhh, more money to spend.

    Perry
    I lost my original Speedhut temp sender and bought a generic one and the autometer adapter. They sent me another temp sender, but it doesn't work with the autometer adapter fitting. I had to order the Speedhut adapter to use with the Speedhut temp sender.
    Big dreams, small pockets....

    Chris--
    '72 Cutlass S LS2/T56 Magnum
    Bowler Performance, Rushforth Wheels, SC&C, ATS, Street Rod Designs, Speedhut, KORE3, Ridetech

    Project Motor City Madness

  10. #10
    Join Date
    Jun 2010
    Location
    Deployed
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    You can buy a coupling to put a sensor in the radiator hose. You can also tap the water pump.
    1970 Camaro/DSE build


    Are you driver enough? Maybe....come on blue!
    https://www.pro-touring.com/threads/...71#post1147371

  11. #11
    Join Date
    Dec 2008
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    Detroit
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    Quote Originally Posted by badazz81z28 View Post
    You can buy a coupling to put a sensor in the radiator hose. You can also tap the water pump.
    Mine is perfect now after the new sender with the proper adapter from Speedhut...
    Big dreams, small pockets....

    Chris--
    '72 Cutlass S LS2/T56 Magnum
    Bowler Performance, Rushforth Wheels, SC&C, ATS, Street Rod Designs, Speedhut, KORE3, Ridetech

    Project Motor City Madness