Dynamo not charging battery. 1955 11BL

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  • 16th February 2025 at 2:43 pm #37005
    Ian Stroud
    Participant

      The dynamo is not charging the battery,  The ammeter does not move except to show a discharge when I turn on the headlights.

      I tested the dynamo; it is producing 7+ volts.  I tried a different voltage regulator…no difference,

      When I connect the BAT terminal of the regulator directly to the + terminal of the battery,  it charges nicely.

      Firstly, is it safe to use this arrangement on a semi-permanent basis, thus by-passing the ammeter?

      Secondly, if I want to check the original wiring, etc. how do I access the back of the ammeter, etc?  There is insufficient room to attack the job from under the dash and I can’t see how I can remove the speedometer panel.

      Ideas appreciated or name of a good auto electrician in the Northampton/Kettering area.

      17th February 2025 at 10:54 pm #37007
      Chris
      Participant

        Hi Ian

        It sounds like you have a break in the wiring somewhere. It’s ok to drive without the ammeter in the circuit – but whether it is safe really depends on the nature of the break. If, for example, a live wire has fallen off something and is flapping around loose, that would not be safe. If it’s a break inside the insulation then it’s ok. So I think you are right to want to investigate further.

        It doesn’t sound like a problem with the ammeter or its connections if it can show a discharge. It must be something in the charging side. The replacement regulator may have the same problem as the original one.

        Checking continuity will be more effective if you can get to the ammeter as it all joins wires together. It will be easier to find a broken wire if you disconnect the wires from the ammeter to buzz them out.

        I don’t have one of these newfangled modern big boot cars with the two-tone dashboard. Taking the speedo out of the earlier cars is quite straightforward but your car hides the speedo behind the windscreen surround.

        966-5

        dash

        What follows is my guess as to how to get to the speedo from looking at the part manual which shows the surround to be in 2 parts. I guess you need to remove the escutcheon covering the windscreen opening mechanism to expose the lower screw and there’s a screw at the top which may or may not be covered. I think there may be some jiggling to release a clip on the side. That should allow the surround to be moved forward for you to get behind it. The speedo is held on the surround by a screw on each side.

        Before you do any of this, of course disconnect the battery. I hope this helps.

        Let us know how it really comes apart and what you find.

        Chris

        20th February 2025 at 11:20 am #37013
        Ian Stroud
        Participant

          Thanks, Chris

          After more fiddling about with the car, I have have taken my generator to Classic Dynamo and Regulator Conversions in Lincolnshire.  The dynamo will be rebuilt “better than the original” and the voltage regulator will be converted to electronic.  I just wanted to be absolutely certain that the fault is in the wiring before I undertake the daunting task of removing the speedo.

          Thanks again for your help.  I’ll update my post when I get the parts back.

           

          25th February 2025 at 2:17 pm #37019
          Bernie
          Participant

            Ian,

            Extracting the instrument cluster is less daunting than it sounds.  Yes, you do have to remove half the windscreen trim but it is a relatively simple job and Chris has pretty well explained the method …. even though he has never done it!

            Plrase contact me if you run into a problem – I’m about 10 minutes away from you.

            B….

             

             

             

            25th February 2025 at 5:01 pm #37021
            Ian Stroud
            Participant

              Thanks, Bernie, for the encouragement.  At the moment I am awaiting the return of my rebuilt dynamo and electronic regulator.  Assuming this work does not solve the problem I will check out the wiring.

              Ian

              19th March 2025 at 6:34 am #37069
              Ian Stroud
              Participant

                Dynamo tested…..working well (and polarised)

                Newly converted to electronic Ducellier voltage regulator

                Wiring dynamo to regulator replaced

                Wiring from BAT terminal on regulator direct to + terminal on battery (which is also new) replaced

                Still no charging voltage getting to the battery.

                When included in the circuitry, ammeter shows no charge, but goes well into discharge when headlights switched on even when engine running.

                What now???

                19th March 2025 at 1:59 pm #37071
                Bernie
                Participant

                  Ian,
                  <p style=”text-align: left;”>You say the dynamo is “working well” – was that a bench test?  If so, have you checked output, both before and after the regulator, with it running on the car?</p>
                  If all is well and charging current is getting beyond the regulator, I would suspect a fault in the wiring thereafter.

                  Relevant wiring diagram can be downloaded from the technical area of the Members Only section of the website.  The one for your vehicle is page 12 of the pdf file

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