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    Temp gauge reading high

    For no apparent reason my engine temp gauge has moved from a pretty static middle of the band to a needles width from red zone. Once there its quite stable, no leaks, kenlowe kicking in as required and testing with IR thermometer gun the temps on block, heads, rad (top & bottom) are all good. Replaced thermostat as i had a new one to hand to discount it but as i guessed no change. Plan to reverse flow flush and clean out system tomorrow once halfords have opened!
    Was wondering if there was a "trim" for the gauge? as ive done that on fuel gauges in the past. Recently had dash in\out a few times chasing bouncing speedo issue and conscious i may have disturbed or disconnected something???

    Thanks in advance
    Rab

    #2
    Hello Rab, because you mentioned the fuel gauge, I suggest that you look at the instrument voltage regulator, as it’s the common power source to both. The regulator lives behind the outer can of the speedo. If you open the bonnet, you will soon smell if the engine is running as hot as the gauge is showing, which you’ve already proved with the checks already done.

    Before you get your hands grubby, look at the instrument voltage regulator. The original regulator operates by a bimetallic gizmo to give the required low voltage (5 volts, I think). I replaced mine with a modern solid state jobbie. If you do fit one, just discard the central pin, and make sure you insulate the other two when wired in.

    Dave



    Comment


      #3
      Is your fuel gauge also indicating higher than it should? If yes, start your search at the voltage stabilizer because it controls both. If this is not the case, check the connection to the temp sensor on the engine and possibly the sensor itself.

      Mel

      Comment


        #4
        I had the same thing happen to me - for me it was a wire had come off the voltage regulator as I had removed the gauges to put in LED lights.

        Jeff

        Comment


          #5
          Had the same problem a few weeks ago. After a mild panic, which was calmed by a quick look under the bonnet to reassure myself that the engine was not running hot. My solid state voltage regulator/stabiliser had failed. Quick swap for a spare and normal temperature restored.
          Dave
          1974 Mk2, ZF Auto, 3.45 Diff, Datsun Driveshafts. Stag owner/maintainer since 1989.

          Comment


            #6
            Quite likely the votage stabiliser has lost it's earth connection, it won't regulate without it.

            Comment


              #7
              On my mk1 Stag there is a separate black ground wire on that back of the speedo. that slides off easily. the VR is attached to the speedo if memory serves me right

              Comment


                #8
                Solid State Voltage Satabilizer mods.docx

                I Think I have a spare as I had to buy a pack of 5 solid state things, will check if so you are welcome to 1 , or you can buy a new stabiliser from one of the stag part suppliers

                ps you dont need the LED in the above mod have a read
                Attached Files
                "The UK,s 2nd Most Easterly Stag" Quad Exhaust- ZF 4 Speed BOX

                Comment


                  #9
                  I you go down the electronic route, be aware there are two components missing in that mods doc - i/p & o/p capacitors, they are required for reliable operation.

                  Also, be aware that the likes of ebay "£7.15 for for 5" will be chinese fakes. Buy genuine Texas Instruments.

                  Comment


                    #10
                    Originally posted by NeilR View Post
                    I you go down the electronic route, be aware there are two components missing in that mods doc - i/p & o/p capacitors, they are required for reliable operation.

                    Also, be aware that the likes of ebay "£7.15 for for 5" will be chinese fakes. Buy genuine Texas Instruments.
                    first time I've heard of that , been use by several on here and the MG folk?, worked on mine
                    "The UK,s 2nd Most Easterly Stag" Quad Exhaust- ZF 4 Speed BOX

                    Comment


                      #11
                      Semiconductor manufacturers don't write datasheets for there products just for fun !.

                      Comment


                        #12
                        As Neil says, the solid state regulators may not achieve their design life (mean time before failure) if they are not protected from transient voltages and noise on the supply, yet owing to the statistical variation of semiconductor failures some examples may well go on for years.

                        I created some calibration charts for my minor gauges so that I'd have a baseline for testing them in future ... hopefully this will help me to find out whether a unusual indication is due to the gauge or the sensor (after eliminating the obvious possibility of a genuine fault, though).
                        temp gauge calibration.jpg fuel gauge calibration.jpg volts gauge calibration.jpg

                        Comment


                          #13
                          Thanks all, turned out to be loose earth connection on back of speedo housing..DOH!
                          Will probably drain and flush system anyway in preparation for summer...potentially a lot of work for one week of decent weather though

                          Comment

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