Fuel Gauge Conundrum

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  • 15th June 2026 at 11:45 am #38391
    David Horsley
    Participant

      My ’51 11 BL was restored in France and has been converted to 12V and has an alternator.

      The fuel gauge reads full at all times except when the tank is entirely empty – I know this because I’ve just de-rusted the tank and operated the sender and gauge on the dry tank.

      The sender unit looks almost new, so I don’t think that’s the culprit.

      I can’t see a voltage reducer anywhere in the wiring, would that be the reason for the false reading or could it simply be a wiring fault at the gauge or the sender ?

      As a side issue, amazingly, my instrument panel clock actually works but runs fast – does that need a voltage reducer as well ?

      15th June 2026 at 1:38 pm #38393
      Bernie
      Participant

        David,

        Fuel gauges are generally Voltage agnostic and have a simple rheostat in the body of the sender.  If the unit is new, I would investigate the wiring.
        <p style=”text-align: left;”>If nothing has been done to either convert the clock to 12V or reduce the voltage to it, there is a grave danger of burning it out.   If it has been made 12V compatible, and the fast running is not excessive, perhaps it simply needs adjustment.</p>
        B….

        16th June 2026 at 12:56 pm #38395
        David Horsley
        Participant

          Thanks very much again, Bernie.

          My car was French-restored and, without wanting to sound Francophobe, I’ve already noticed a couple of other unusual Gallic approaches to the wiring installation.

          I’ve found the French instructions for fitting the sender amongst the car’s paperwork and the in situ wiring doesn’t look like the diagram provided, so I’m going to correct that.

          I think it won’t do any harm to fit a heavy duty 12V/6V converter and run the clock and the presently unconnected wiper motor through it because there’s nothing to suggested that their voltage has been modified.

           

          16th June 2026 at 2:27 pm #38397
          Bernie
          Participant

            <p style=”text-align: left;”>Clock and wipers won’t need a particularly heavy 6V converter.   There are plenty on the internet with outputs of around 10 Amps which will be adequate.</p>
            Citroën Classics also offer a suitable unit and you will get your 10% discount if you quote the code in their FP ad.

            Screenshot_20260616_141742_Chrome

            B….

            20th June 2026 at 4:47 pm #38545
            David Horsley
            Participant

              Hi Bernie,

              I’ve disconnected the sender and the gauge still reads full !

              I’m guessing a voltage reducer for the gauge is needed, but it’s amazing that the gauge and the clock  haven’t burned out in the 15 years since the restoration.

              The wiper motor isn’t functioning and I’m relying on Rainex at the moment but I’ll get a converter strong enough to cope with that too – I hope that hasn’t burned out.

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