D special: ‘Pulsating’ lights
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  1. #1
    Fellow Frogger!
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    Default D special: ‘Pulsating’ lights

    Dear brains trust

    The lights (both interior and headlights) on my D special ‘pulsate’, or vary in their brightness.

    A quick google search suggests that this could be related to battery connections and grounds (clean and tighten etc) and/or to alternator bushes or the regulator.

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    I will go over connections etc first, but is there anything particular to a D that might be applicable? In what order should I be eliminating possible causes?

    Regards

    AM

  2. #2
    Fellow Frogger! citroenthusiast's Avatar
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    Probably the mechanical voltage regulator. It oscillates between a low and high charge setting to keep the battery at approximately 14.7 volts. Replace it with an electronic regulator (e.g. Ford Mustang) and the pulsing will likely go away.
    Cheers,
    John T.

    54 TAV Legere; 61DS19 LHM BVH (son's); 71DS21 BVH; 73SM 3.0; 73SM EFI (Megasquirt); 73SM 3.0 (other son's)

  3. #3
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    AM,
    I had the exact same problem and I had a Bosch electronic, 2-wire regulator.
    As was explained to me, it was caused by a slightly unstable regulator reference voltage (because the circuit came via the instrument panel and a few volts might have "got lost")
    The easiest solution was to put a relay in with a feed coming direct from battery. It fixed the problem immediately
    I can send you the circuit if you want.
    Cheers
    Ian Downie
    Blueduck (aka Ian Downie)
    1974 Citroen D Special with DS21i.e. engine and 5 speed gearbox
    MGB GT V8 B.... bullet--proof and great fun
    Jaguar e-type roadster ... on the way from US of A

  4. #4
    Fellow Frogger!
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    Hi a

    my solution was to replace the alternator with a new one with an internal regulator. Not very expensive, hard to tell the difference and very reliable. Got mine from atelier 524

    peter

  5. #5
    Fellow Frogger! Don B. Cilly's Avatar
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    Default

    See also here.
    Even though... in the end... if the battery gets properly charged (you may want to get a $5 voltmeter and stick it in the lighter socket) a bit of flickering does go with the territory
    They have a pulse, they have a soul...

    If it doesn't, or if it bothers you, new alternator with new regulator, will fix it.

  6. #6
    Fellow Frogger!
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    Quote Originally Posted by blueduck View Post
    AM,
    The easiest solution was to put a relay in with a feed coming direct from battery. It fixed the problem immediately
    I can send you the circuit if you want.
    Cheers
    Ian Downie
    I'd be interested in seeing the diagram Ian. Can you put an image up with a post here perhaps?

    Budge
    1968 DS21bvh Pallas in Gris Palladium

    Restoration blog: https://ds-restoration.blogspot.co.uk

  7. #7
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    D special: ‘Pulsating’ lights-alternatorwiringdiagram-installed-4-comp.jpg

    It was clearer to me 3 years ago but that is it.
    Note The new and additional regulator and the connections to it
    Note external Bosch regulator ... just 2 wires.
    Note the wire you must cut
    Cheers
    Ian
    Blueduck (aka Ian Downie)
    1974 Citroen D Special with DS21i.e. engine and 5 speed gearbox
    MGB GT V8 B.... bullet--proof and great fun
    Jaguar e-type roadster ... on the way from US of A

  8. #8
    1000+ Posts Ken W's Avatar
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    The case of the RE55 needs to be well connected to chassis or battery negative and it is best mounted close to the battery with the relay.

    Cheers, Ken

  9. #9
    Fellow Frogger!
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    Quote Originally Posted by blueduck View Post

    It was clearer to me 3 years ago but that is it.
    Note The new and additional regulator and the connections to it
    Note external Bosch regulator ... just 2 wires.
    Note the wire you must cut
    Cheers
    Ian
    Thanks Ian. I think i get it. I'm working with an original external Ducellier VR and my car's not an efi, but I think i get the principle. I can see where the wire that would have run from the ignition to the Bosch has been cut and taken off to the relay instead.
    1968 DS21bvh Pallas in Gris Palladium

    Restoration blog: https://ds-restoration.blogspot.co.uk

  10. #10
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by blueduck View Post
    AM,
    I had the exact same problem and I had a Bosch electronic, 2-wire regulator.
    As was explained to me, it was caused by a slightly unstable regulator reference voltage (because the circuit came via the instrument panel and a few volts might have "got lost")
    The easiest solution was to put a relay in with a feed coming direct from battery. It fixed the problem immediately
    I can send you the circuit if you want.
    Cheers
    Ian Downie
    I had an identical problem and was suggested an identical solution. It was and is an Australian Bosch alternator in a Renault R8. I used the feed voltage to the regulator (from the ignition switch) to operate a relay that switched 12V from the positive on the alternator to the regulator (30 cm wire length) and the problem disappeared. It happened with both old-school regulators and newer solid state ones.
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Peugeot 306 XT 1995 (daughter's)
    Citroën CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  11. #11
    Fellow Frogger! citroenthusiast's Avatar
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    Many years ago, I wrote an article describing how to install a Ford voltage regulator in a DS BVH. For BVM (an SM) it is much simpler since you don't have to worry about the starter inhibit circuit. One advantage of the Ford (and possibly other) regulators is you can wire the "A" terminal directly to the battery (or the battery post on the alternator) since the Ford VR self-energizes through the indicator light to close the high current field relay (transistor, actually). This means the field current is no longer sourced through the ignition switch.
    D special: ‘Pulsating’ lights-voltage-regulator-article-a2_page_2.jpg
    D special: ‘Pulsating’ lights-voltage-regulator-article-a2_page_1.jpg
    Cheers,
    John T.

    54 TAV Legere; 61DS19 LHM BVH (son's); 71DS21 BVH; 73SM 3.0; 73SM EFI (Megasquirt); 73SM 3.0 (other son's)

  12. #12
    Fellow Frogger! citroenthusiast's Avatar
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    Here is an enlarged diagram showing the Ford VR in place of the original. Optionally disconnect and insulate the ignition switch lead ("BOB") to the VR (broken line in the diagram) and wire the VR directly to the battery (red line in the diagram) using a 30A fuse. This allows the field to be energized directly from the battery without going through the ignition switch.

    D special: ‘Pulsating’ lights-voltage-regulator-article-wiring.jpg
    Cheers,
    John T.

    54 TAV Legere; 61DS19 LHM BVH (son's); 71DS21 BVH; 73SM 3.0; 73SM EFI (Megasquirt); 73SM 3.0 (other son's)

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