Fuel/Water Temp Gauge Issue Found! Now what...

Electrical and Ignition

  1. Righty Tighty

    Righty Tighty Well-Known Member

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    So, neither my fuel gauge nor the water temp gauge was working when I bought my 71 Scamp. I tried a new fuel sender to troubleshoot, no change. Today I removed the instrument cluster to get to the bottom of it, and saw a broken piece of circuitry leading to the fuel/water temp gauges. I don't know what the circuitry part is called, if anyone knows please chime in.

    Anyway, I'm almost certain this is what caused the issue. My question is, how do I fix it? Can this be soldered? My guess as to what caused it is maybe a bare wire somewhere touched it and shorted. fullsizeoutput_75c.jpeg
     
  2. cudascott

    cudascott wish I had a Hemi

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    That will do it every time! You could find try to find another board or just scrape the coating off the circuit on each side of the break and solder a jumper wire in.
    Also remove or reattach that part that’s came loose from the board.
     
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    • Dana67Dart

      Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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      Easy fix as cudascott said.
      Just clean both sides of the brake and use a small bit of wire to bridge the gap. Tin both sides of the trace and both ends of the wire before you solder it all back together.

      You can also buy a reproduction cir board.

      Lastly make sure you cluster has a IVR (voltage regulator) installed and working.
       
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      • 67Dart273

        67Dart273 FABO Gold Member FABO Gold Member

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        Don't stop there. More work to be done, you can fix it

        I think this is the old thread on board repair, but the photophhphphphucket has crapped on the photos

        Printed circuit pins repair

        General idea:

        Harness connector pins. Clean them and solder the pins to the board traces

        Solder jumpers across the spring clips that make contact with the IVR. The fingers lose contact with the board traces

        Loosen/ tighten the gauge stud nuts several times as they get corroded

        Add a ground pigtail to a ground point on the board and bolt the other end to a ground such as column support.

        Buy yourself a solid state replacement for the IVR

        Use big eraser to buff clean the copper where the bulb sockets contact, and be sure the spring contacts are in good shape and clean

        BE CAREFUL!!! DISCONNECT the battery!!! The BIG BLACK and BIG RED ammeter wires are both always HOT!! They are NOT fused

        DSC_1420_zps45673b88.jpg

        DSC_1421_zpsa3d00147.jpg

        NOTICE!! THE ABOVE ARE NOT MY PHOTOS THEY came from the 'lost thread' with the lost photobucket photos
         
        Last edited: Feb 15, 2020
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        • moparmat2000

          moparmat2000 FABO Gold Member FABO Gold Member

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          In your first pic on the right the rectangular box is the IVR. This is a points type unit with a heated bimetal spring. It opens and closes continuously with ignition on to drop your 12V electrical down to 6V to run the fuel level, water temp and oil pressure gages. You can buy yourself a solid state IVR for about $25 as a plug n play and be done with it, or make one if your electronically inclined for about $5. Heres a schematic below. I have built these up for both my 67 and my sons 69. Nice evening workbench project.

          Screenshot_2016-12-28-22-20-08.png
           
          Last edited: Feb 14, 2020
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          • moparmat2000

            moparmat2000 FABO Gold Member FABO Gold Member

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            Also solder the pins to the copper tracings, and on the back sides of the pins where they are hollow, after 50 years this stuff tends to get loose. I cut down small brass coated brads that I got at lowes and glued them inside the pins from the side where the pins are crimped over with super glue. This helps prevent the pins from loosening and coming apart from the board. When doing this make sure theres still clearance between the heads of the brads and the metal gage housing since that metal housing is a ground point. You can file the heads of the brads flatter, or clearance the back of the cluster housing.
             
          • Kendog 170

            Kendog 170 Well-Known Member

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            Check repair made in this pic upper right of red circle.
            fixed_pin-jpg.jpg
             
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            • moparmat2000

              moparmat2000 FABO Gold Member FABO Gold Member

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              Heres a pic of a homemade Solid State IVR on my rallye dash. On rallye dashes the IVR is inside the gas gage and must be disabled leaving the gage portion to work. On a dart or any non rallye dash, you would use male spade connectors and plug in at stock location. Note the dielectric grease under the chip, and chips mounting tab is also a ground. Chip will take up to 35 VDC and reduce it to 5.5 VDC so asking it to drop 13.5 VDC to 5.5 isnt asking much of it.

              20150905_180220 (1).jpeg

              20150905_180220 (1).jpeg

              downloadfile-7.jpg

              images-8.jpg
               
            • RedFish

              RedFish Well-Known Member

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              What we're seeing is the copper trace serving as a fusible link. The root cause is guesswork. Good luck with it.
               
            • Righty Tighty

              Righty Tighty Well-Known Member

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              Funny you mention the solid state, prior to removing the cluster I had been reading up on troubleshooting the fuel/temp gauge failure. Seems the most common failure is the voltage regulator, and since it wasn't my fuel sender or a bad ground, that was my next plan of attack. I found some solid state IVRs and it seemed like a good retrofit, and you mentioning it just confirms that it's a good way to go.

              Agreed. The wiring behind the cluster didn't seem too bad, but I guess all it takes is one bare wire or piece of metal to short it. Unless there was a power surge somewhere that a fuse didn't catch?
               
            • RedFish

              RedFish Well-Known Member

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              Prior to 1972 model 12 volt supply to inst' panel/instrument voltage limiter wasn't fused other then the main fusible link outside the bulkhead connection.
               
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