Citroen DS headlight switch testing
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  1. #1
    Tadpole
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    Default Citroen DS headlight switch testing

    Hi,

    I'm new to Citroens but I do have some experience with other classic cars. I'm trying to help a friend figuring out why the headlights on his DS are not working. I started with testing the switch. While testing it, with the ignition turned off and the switch in the off position I have 12v on all wires except the yellow one. That one showed 6v. Is that the way it is supposed to be?

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    I've attached an image of the back of the switch in case there are different versions.

    Cheers,

    Wim

    Citroen DS headlight switch testing-img_0985.jpg

  2. #2
    Fellow Frogger!
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    Hi from the UK Wim.

    If you've found your way to the switch and the yellow wire, then I assume you're ruling out a blown fuse as the problem? Equally ruling out dirty connections at the fuse? The switch looks to be from a 1969 or later car. If you download a pdf of volume 1 of Manual 814, you will find a circuit diagram for the various versions/ years of cars.

    There was a thread here on Aussie frogs some time ago that looked at wiring problems and included headlights. It was called "DS21 dashboard". it covers a lot of messages but eventually gets round to discussing headlamp wiring connections.

  3. #3
    Fellow Frogger! Don B. Cilly's Avatar
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    Yes, see here.
    Yellow goes to the relay for high beam.
    If it shows 6V... it could be that the relay was bypassed and the wire can't carry enough current - hence the drop in tension.

    Except... you say you have tension on all wires with the switch in the off position?
    You should have 12V on the black wire, and then get it on the other ones as you turn it accordingly - they go directly to the lights, except the yellow one that goes to the high beam relay.

  4. #4
    Tadpole
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    Quote Originally Posted by Don B. Cilly View Post
    Yes, see here.
    Yellow goes to the relay for high beam.
    If it shows 6V... it could be that the relay was bypassed and the wire can't carry enough current - hence the drop in tension.

    Except... you say you have tension on all wires with the switch in the off position?
    You should have 12V on the black wire, and then get it on the other ones as you turn it accordingly - they go directly to the lights, except the yellow one that goes to the high beam relay.
    thanks, still researching. It definitely looks like the previous owner has made modifications to the wiring harness. Where would I usually find the high beam relay? I'm starting to believe it might not be on the car anymore as so far I have not been able to find it.

    I'm experiencing all sorts of weird things, like when I try to turn on the long range head lights, the horn goes off....

  5. #5
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    hello,
    1 An obvious comment but I always miss the obvious when trying to fix my own D Special. There is an earth connection on both left and right side and they are connected to chassis next to the headlamps, The earths go back the light wiring loom and 1 connection each side serves all the various lights on that side. When one of my earths was dodgy all sorts of strange thinks happened .. just like you are experiencing

    2 My D Special (1974) never seemed to have headlamp relays. But the lights worked OK without them. But I wanted to protect the switch and the old wiring so it now has 2, one high beam (for both sides), one directional lamps (for both sides), none on low beams. The lights are brighter as you might expect

    3 Why not check the voltage at the lamps... should be about 12 (for all lights) depending on battery charge. If it is 6 as you have measured at the switch it suggests it is not a relay problem I think ... not entirely sure about that. But disconnect wire going to light and check again

    4 If there is a relay, you should be able to hear it click in (unless it is totally faulty ... in which case why the 6 volts)

    5 Is the yellow wire switched "on" or is it coming coming directly from battery. It looks a heavy duty cable which suggest it goes direct to lights without relay (but thru fuses). I am guessing here. But I assume a light relay circuit would have a permanent heavy duty connection (the yellow cable??) to battery (possibly fused) and the activating wire, coming from switch, does not need to be so heavy duty. I should check the circuit diagram before I make these comments but the circuit diagrams I have never seem to match up with what is on my car

    6 Finally, some of these light have (inline) fuses. Worth finding and checking as someone else alluded too. I had terrible trouble with mine until I cleaned and cleaned and cleaned all the fuse connections

    I should say electrical things try both my knowledge and my patience

    Regards
    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

  6. #6
    Fellow Frogger! Don B. Cilly's Avatar
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    Quote Originally Posted by miami_ds View Post
    Where would I usually find the high beam relay?
    Usually just behind the diver's air grill. You can get at it with your hand just by removing the instrument panel, but I'm not sure you can see it, even with a mirror, without removing the whole dash.

    Looks like this:



    I'm experiencing all sorts of weird things, like when I try to turn on the long range head lights, the horn goes off....
    Well the horn could just be a crossed wire (horns are usually blue and white sleeve wires - you have two horns) but...
    you often get all sorts of weird things if your ground connection is bad - and it often is.

    So check the grounds. Brown sleeve wires, near the lights themselves.
    Run a temporary - you can actually make it permanent, the more the merrier - wire from the ground point on the lights to the chassis, and see if things get less weird.
    They may well do

    The relay, if it doesn't work, you can use any 30A - or more - thing.
    Last edited by Don B. Cilly; 12th September 2017 at 08:27 PM.

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