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  • Temperature Gauge Reads Low

    I've been trying to figure out why my temp gauge reads low. The wire leading from the sending unit is really thick compared to most other wires in the electrical system. It's obviously not stock. Could this be the problem? I've replaced the voltage stabilizer and the gauge. I also have a new sending unit, but haven't installed it. I don't believe the car is actually running cool. I've not found an answer in Dan Masters' manual.


    Click image for larger version

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    Attached Files
    Pete, Collierville TN
    1976 CF54385 U
    A rolling resto in progress...

  • #2
    There are different sending units, ........and different gauges. Mixing them up changes things.

    Comment


    • #3
      Have you measured the actual temp near the sender?
      1973 TR6 – BRG with beige interior, custom LED lighting
      Hardtop, OD, Rollbar, 15”Koenigs
      Bored, balanced and polished motor with Kastner/TSI S2 Cam
      Header, custom exhaust, custom alternator, e-fan
      Lowered, poly suspension, Konis and rear anti roll-bar
      www.coventrysfinest.blogspot.com

      Comment


      • #4
        I've had 2 sending units go bad; the one that was in the engine when I bought the car and a spare that came with the car....How did I know it when they went bad ?
        The gauge began reading lower than normal.
        I just checked and it's Out of Stock right now, but the black top one from BPNW was compatible with my gauge.
        Driving a 1973 TR6
        Doing ZS carb repairs
        email kencorsaw"at"aol.com

        Comment


        • #5
          Originally posted by oppositelocksmith View Post
          Have you measured the actual temp near the sender?
          Yup. ~ 180 deg.
          Pete, Collierville TN
          1976 CF54385 U
          A rolling resto in progress...

          Comment


          • #6
            Originally posted by poolboy View Post
            I've had 2 sending units go bad; the one that was in the engine when I bought the car and a spare that came with the car....How did I know it when they went bad ?
            The gauge began reading lower than normal.
            I just checked and it's Out of Stock right now, but the black top one from BPNW was compatible with my gauge.
            Thanks, Ken. I just checked my replacement unit and it's a black top GTR108, same as the BPNW unit. I also discovered that the wire I mentioned in my original post is not thicker. It just has an extra insulator shield around it. Once the engine cools, I'll install the new sending unit and see what happens.

            OBTW, the carbs are performing beautifully! The choke issue I was having was just me needing to relearn what setting was required. Unless it's cold outside, little to none is needed at all.
            Pete, Collierville TN
            1976 CF54385 U
            A rolling resto in progress...

            Comment


            • #7
              Originally posted by prasnick View Post
              I've been trying to figure out why my temp gauge reads low. The wire leading from the sending unit is really thick compared to most other wires in the electrical system. It's obviously not stock. Could this be the problem? I've replaced the voltage stabilizer and the gauge. I also have a new sending unit, but haven't installed it. I don't believe the car is actually running cool. I've not found an answer in Dan Masters' manual.


              Click image for larger version

Name:	06A03A74-7E31-4166-A830-C59996DC0155.jpeg
Views:	197
Size:	1.99 MB
ID:	529490
              Since you know that the actual temperature of the coolant is at 180deg. I'd say it's the sending unit that's inaccurate. After a systems overhaul a few years back this included a new sender. It showed the gauge engine running temp. to be close to 200. I replaced it with one from another supplier. It showed 190 under the same conditions. I then reused the one from before all of this work was done. It read right up against the left side of the middle mark on the temperature gauge, just as before. This was confirmed using an infra red hand held gun.

              Dick

              Comment


              • #8
                I installed the new sending unit, and the results are inconclusive. After a drive, I took the following temperature measurements on the water pump body adjacent to the sender:

                180 deg., engine fully warm and running.

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                190 deg., engine fully warm, key on, engine not running. Taken 2-3 minutes after shutting engine off.

                Click image for larger version

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                Engine cool.

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                Questions:
                Is 180 degrees a "normal" operating temperature (180 degree thermostat installed)? Could the gauge be calibrated a little low? The needle is bottomed out to the left of the C mark when the engine is cold. I don't remember my old gauge reading that low. Is this really an issue at all? I'm starting to think not. It just bugs my OCD self that the needle isn't on the middle mark when the engine is fully warmed up. Discuss.
                Attached Files
                Pete, Collierville TN
                1976 CF54385 U
                A rolling resto in progress...

                Comment


                • #9
                  180 t-stat also.
                  I don't know the exact temperature, but on my gauge the needle stabilizes in the same position as yours in your first picture when I'm just cruising around
                  In your 2nd picture, that's about where my needle is when the electric fan kicks on ...usually due to prolonged idling.
                  Driving a 1973 TR6
                  Doing ZS carb repairs
                  email kencorsaw"at"aol.com

                  Comment


                  • #10
                    This looks normal to me. The gauge is not built with numbers, so it is calibrated to whatever tick mark it matches.
                    1973 TR6 – BRG with beige interior, custom LED lighting
                    Hardtop, OD, Rollbar, 15”Koenigs
                    Bored, balanced and polished motor with Kastner/TSI S2 Cam
                    Header, custom exhaust, custom alternator, e-fan
                    Lowered, poly suspension, Konis and rear anti roll-bar
                    www.coventrysfinest.blogspot.com

                    Comment


                    • #11
                      Originally posted by prasnick View Post
                      I installed the new sending unit, and the results are inconclusive. After a drive, I took the following temperature measurements on the water pump body adjacent to the sender:

                      180 deg., engine fully warm and running.

                      Click image for larger version  Name:	IMG_8374.jpeg Views:	19 Size:	2.57 MB ID:	529508

                      190 deg., engine fully warm, key on, engine not running. Taken 2-3 minutes after shutting engine off.

                      Click image for larger version  Name:	IMG_8377.jpeg Views:	19 Size:	2.64 MB ID:	529510

                      Engine cool.

                      Click image for larger version  Name:	IMG_8373.jpeg Views:	19 Size:	3.20 MB ID:	529512

                      Questions:
                      Is 180 degrees a "normal" operating temperature (180 degree thermostat installed)? Could the gauge be calibrated a little low? The needle is bottomed out to the left of the C mark when the engine is cold. I don't remember my old gauge reading that low. Is this really an issue at all? I'm starting to think not. It just bugs my OCD self that the needle isn't on the middle mark when the engine is fully warmed up. Discuss.
                      If your temperature gauge rested as mine did, I think the needle would butt up against the center mark when at 180 deg. The needle is probably adjustable from its resting position.

                      Dick Click image for larger version  Name:	Dash + 5 speed shift knob.JPG Views:	0 Size:	2.65 MB ID:	529519
                      Attached Files
                      Last edited by dicta; 03-07-2020, 02:07 AM.

                      Comment


                      • #12
                        Thanks for the comments, everyone. I think it's safe to say that my cooling and indicating systems are working normally. Next time I have absolutely nothing better to do (probably won't happen in this lifetime), I'll take the gauge apart and adjust the needle a little to the right.
                        Pete, Collierville TN
                        1976 CF54385 U
                        A rolling resto in progress...

                        Comment


                        • #13
                          Orrrr Pete you could get one of the Smiths gauges w a capillary connection. They’re gonna give you a more accurate reading. I believe BPNW sells em new or they can be had off MG midgets or bug eyes or maybe MGAs. Actually what bpnw sells along w MG bits are dual Water temp & Oil PSI so you can free up space for other cool stuff. Vacuum or something like that. C’mon let’s spend some money!!
                          So much rust, so little time

                          64 TR4 Overdrive Surrey
                          67 GT6 Mk1
                          68 TR250 Soon to have Overdrive & Surrey
                          71 TR6 Hardtop Soon to have OD
                          81 TR8 Injected Automatic...the LAST Automatic

                          Comment


                          • #14
                            Originally posted by tr250 View Post
                            Orrrr Pete you could get one of the Smiths gauges w a capillary connection. They’re gonna give you a more accurate reading. I believe BPNW sells em new or they can be had off MG midgets or bug eyes or maybe MGAs. Actually what bpnw sells along w MG bits are dual Water temp & Oil PSI so you can free up space for other cool stuff. Vacuum or something like that. C’mon let’s spend some money!!
                            You funny guy.
                            Pete, Collierville TN
                            1976 CF54385 U
                            A rolling resto in progress...

                            Comment

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