Alternating alternator...
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Thread: Alternating alternator...

  1. #1
    WRB
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    Default Alternating alternator...

    Hello

    The dash lights on the CX alternate between dim and bright fairly slowly at idle and speed up at higher revs. I have checked the battery with the engine both stopped and idling and, both readings are good (12.8 on the battery and 14. something with the motor running). Could this be caused by the voltage regulator or, is it just stuffed wiring....

    cheers

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    Warren

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    Contented Peugeot Driver addo's Avatar
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    Try putting more load on the alternator. Heater blower on full, lights on high beam, press a window switch up and hold for a second, see if the head lights dim.
    Hotrodelectric and jaahn like this.

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    WRB
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    They dim... stuffed alternator?

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    Now go make me a sandwich Hotrodelectric's Avatar
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    It appears you're getting a proper charge rate, so first off carry out the checks that Adam suggested. How old is your CX? That will tell me if you have an internal or an external regulator. Unfortunately, the wiring probably isn't stuffed (I'm assuming it hasn't been screwed with over the life of the car), but down around the battery is one hell of a rat's nest to check out, especially when checking for grounds. In addition to Adam's suggestion, check both ends of both battery cables for cleanliness and tightness, and if the individual strands at the cable ends are breaking or corroding. Check the alternator belt and make sure the belt is properly tensioned and in good repair.

    Remember- simple and stupid first, THEN dig deeper.
    The measure of your character isn't what you do when people are watching- it's what you do when they aren't watching.

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    Now go make me a sandwich Hotrodelectric's Avatar
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    Quote Originally Posted by WRB View Post
    They dim... stuffed alternator?
    Possibly, but let's not panic just yet.
    The measure of your character isn't what you do when people are watching- it's what you do when they aren't watching.

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    Real cars have hydraulics DoubleChevron's Avatar
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    Is the CX late enough to have the 100amp paris rhone alternator and rectifier "block" out in front of the radiator. If so you'll likely find dead/cremated wires out to the rectfiier that is full of dead diodes......

    That setup never worked very well. If the headlight switch isn't relayed, expect it to go up in smoke at some point on you

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    WRB
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    It is a 76 model with an external regulator. Most of the wiring that I have dealt with so far has been brittle and corroded so, I am considering building a new under-bonnet harness. It has a new positive battery lead. I have had to re-wire the headlights to get everything working properly and, of course, people who owned this car in the past have just cut of the ends of leads loosing the colour code sleeves in the process so, any work that should be simple, requires a multimeter and a lot of patience. There are a lot of wires that don't go anywhere - they just sort of hang in the air with the terminals cut off. I can only assume that, as everything is working, (after a fashion) that Citroen put them there to confuse would-be amateur auto-electricians....

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    WRB
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    If I replace it Shane, it will be with an alternator that has the regulator built in. I haven't removed the Alt so, have no idea of the make. I think the regulator is in the engine bay rather than in front of the radiator - I will pop down and have a look.

  9. #9
    Real cars have hydraulics DoubleChevron's Avatar
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    It's easy to pick, if you have the paris rhone setup you will have 6 chunky wires running out of the back of the alternator ( as it's a 3phase device).

    Yes best fix is the throw the old alternator away and fit a modern internally rectified and regulated alternator in it's place.

    There is huge voltage drop through the wiring on a CX, so do your checks at the battery.

    seeya
    Shane L.
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    '63 ID19 http://www.aussiefrogs.com/forum/showthread.php?t=90325
    '72 DS21 ie 5spd pallas (last looked at ... about 15years ago)
    '78 GS1220 pallas
    '92 Range Rover Classic ... 5spd manual.

    Yay ... No Slugomatics


    Modern Junk:
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    WRB
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    The conversion may already have been done.... I have the positive lead to the battery and a couple of thin black wires coming off the other terminal.

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    1000+ Posts 504-504-504's Avatar
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    On a 504 I had at one time the lights would flicker when the engine was idling.
    Wouldn't start one morning.
    Lifted the bonnet to find some nice little copper ingots nestling in the block and the positive wire from alternator to battery no longer in attendance.
    My guess was that the alternator had a short at a certain point of its rotation.
    Russian Roulette but it took a few months.
    Very lucky that the car didn't catch fire.

    Paul.
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    1000+ Posts Greg C's Avatar
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    Even with a known good internally regulated alternator I still get a bit of dimming of the lights at very low engine revs. Let the engine idle, and then switch on the lights. Do engine revs drop because of the extra load? If so I would say your alternator is OK.

    Other thoughts, the battery. If it measures a good voltage that doesn't mean it is OK. Needs to be load tested. Check the water pump. The SKF replacement from CX basis has smaller double pulleys 85mm versus 100mm so the water pump spins faster and therefore the alternator and air-conditioning compressor. If yours has 100mm diameter pulleys order a replacement from CX Basis. You will need it soon anyhow probably.

    In the interim, turn up the idle speed a bit
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    Quote Originally Posted by WRB View Post
    If I replace it Shane, it will be with an alternator that has the regulator built in. I haven't removed the Alt so, have no idea of the make. I think the regulator is in the engine bay rather than in front of the radiator - I will pop down and have a look.
    The original regulator on the early cars was a device that clipped into a specially designed battery case that had two flanges for the reg. to slide into! You can't get a battery like that any more so Bruno from Citro Motors used to cut these off the old batteries ( plastic case ) and screw them to the inner guard as a mount for the original regulator. This is how my car is set up. There is a solid state replacement available that was often used when the original died. I have one of these fitted to my GS in place of the original ( same as the original CX unit ) and this works well.
    My CX lights pulsate the same as yours when idling and the GS does not any more!
    Tends to make me think that it is just the design of the regulator originally fitted! I am just going to live with it! I have rebuilt the alternator, all the wiring and various relays so it must be the old design of the reg! It is fine when running above idle speed!
    Incidentally you will find that the covers pop off the relays and you can check their operation visually as well as electrically!
    Cheers Gerry

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    WRB
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    I will just live with it Gerry - everything works and, as soon as you rev the engine everything stabilises (unlike on the xm - the headlights have a constant flicker). Going for a roadworthy on Tuesday to a guy who is fixing the exhaust and has had absolutely nothing to do with hydropnumatic Citroens in his life. This should be interesting....

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    1000+ Posts gerrypro's Avatar
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    Make sure that he does not pick you on the "Non Working" self cancelling indicator switch! I had to produce proof that this was never fitted on Citroens until they produced the BX!
    Let us know how you get on!
    Cheers Gerry

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    1000+ Posts Ken W's Avatar
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    These old CXs had a voltage regulator that worked more like that on an old generator unit. You get full field current until the battery reaches max voltage, then the reg switches down to a much lower field current that is designed for running at high revs. GSs were the same. So its pretty much all charge or not much.

    I was quite common to fit an external electronic bosch regulator instead of the relay type unit as these would infinitely vary the field current to get a more constant battery voltage of about 14 volts - so long as it was a good installation and didn't go unstable. Let me know if you want more details on the Bosch reg modification.

    Just writing this is making me feel like I should get down there and fire up the old CX wagon. I need to get it pumped up and on blocks so I can try out that other starter motor (the current one only works about every third turn of the key). But sitting here listening to Coldplay up loud is pretty cool.

    Cheers, Ken W

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