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    Question about installing a water temp gauge.

    I am going to buy a water temp gauge soon in an effort to try to get more exact information on the just how warm my coolant really gets since the stock water temp gauge in the cluster says jack-diddly....

    My question is..... can anybody share with me a good location for installing the sensor? Or, should I just try to use the sensor that the stock water temp gauge is using? Does that work? Can I just "piggy back" on it and have both gauges going? Will it read accurately if I use the current sensor already in the car?

    Anybody else already install an aftermarket water temp gauge?

    Your help is appreciated.

    Larry

    #2
    I grabbed a spare thermostate housing from the junkyard and drilled and tapped a hole in it and it works great.

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      #3
      Originally posted by roymacavoy View Post
      I grabbed a spare thermostate housing from the junkyard and drilled and tapped a hole in it and it works great.
      Now there's a thought.....

      Thanks for the idea. I'll look into that.

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        #4
        Anybody else try anything dif? Anybody try just piggy-backing the wires? Did it work well?

        Haven't had time to attempt anything yet, so I'm fine with data collection at this point.

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          #5
          Piggy backing the wires to the stock temperature sensor will give inaccurate readings, as the resistance after the temperature sensor to ground will be equal to 1/(1/rgauge1 + 1/rgauge2), or about half the resistance. Each gauge will also see the resistance of the other gauge to ground as a temperature reading. For example, if you have a 100 ohm RTD at 100 ohms, and 100 ohms of input resistance on the stock gauge, the aftermarket gauge will see 50 ohms when it should be seeing 100.

          The gauge will need to read the temperature from the RTD it is calibrated to.

          Edit: This might not be a problem with super high resistance gauges, I have no idea what the stock gauge input resistance is, though I would imagine it would be fairly rudimentary lowish resistance.
          Last edited by DuRWooD; 07-30-2011, 02:26 PM.
          sigpic
          1992 Familia GT-X
          1988 323 GTX
          2011 F150 Lariat Ecoboost
          2014 Civic Touring

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            #6
            Where did you copy/paste that from? LOL

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              #7
              I'm an instrumentation engineer.

              Well, I'm an instrumentation engineering technologist. Not a real engineer, lol.
              Last edited by DuRWooD; 07-30-2011, 04:07 PM.
              sigpic
              1992 Familia GT-X
              1988 323 GTX
              2011 F150 Lariat Ecoboost
              2014 Civic Touring

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                #8
                i used a small piece of pipe that fit in the radiator hose found a nut that fit the sensor drilled the pipe and welded the nut to it cut the hose slid in and secured it with a spare hose clamp.
                1989 bf b6 hatch. dead
                1992 maz 323 project rally. dead

                1991 mazda protege custom cai
                2.5 inch exhaust in to magnaflo dual tip muffler
                bp swap obx stainless header exintake miata 10.1 pistons and megasquirt comming real soon




                sigpic

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                  #9
                  Yeah you will most likely run into issues using an aftermarket gauge with a stock sensor. Like Durwood said the resistance will be different and the gauge will read way off.

                  I hooked up an autometer gauge to a stock KL sensor, and it was reading around 240 degrees on a semi-warmed up motor. Put in the autometer sensor right after and it dropped down to 160-ish.


                  '88 323 sedan, K-swapped..

                  '03.5 Mazdaspeed Protege - miss it so much..

                  '01 Dodge Ram 3500 Cummins - 323 hauler

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                    #10
                    Excellent info. Thx. I knew you guys would know what to do. I guess I'll probably be trying the idea of finding a back-up water jacket and drilling a new hole in order to install a second sensor (the one that comes with the autometer gauge) or just use the existing hole from the stock sensor if it's the right size (diameter and threading) I wish I were so lucky.... I'll let you guys know how things work out when I get around to attempting this. I just got back from another wedding (two weekends in a row). Can't wait until things settle down. Have to take my youngest to the airport tomorrow for his trip to Europe. Then, I get to go to my niece's digs to help with gift opening from the wedding. Can't even find the time to train on my bike..... sheesh.

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                      #11
                      Your stock gauge sensor larry is the small 1 wire sensor just behind the thermostat facing the fire wall...

                      The sensor on the end of the thermostat hosing facing the fender is for fan control

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                        #12
                        I've also heard of the sensor getting heat soak if its in the thermostat housing. I'd do what 89bfb6 said.
                        -Steve

                        94' Protege < Worklog<SOLD!
                        VF10 powered!
                        262 Whp & 257 Wtq
                        13.1@107

                        '02 Suzuki Bandit 600s

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