Alternator problem - help needed

Discussion in 'How To' started by Dave Goddard, Apr 9, 2024.

  1. Hi guys, hope you can help. Vans been pretty good since engine debarcles, did a three weeker to portugal last year, and all was well. Just did a service and all fine. Went for a drive and the alternator light has come on. Drove it back and stuck a meter on the peg on top of tge alternator to ground on the van and dont have more than the bat voltage with the engine off. As the alternator is just windings, i.e. no wear out parts, am i right in saying it could be the internal regulator ? If so any ideas how to check with the alternator in situ and how to change it? I am loathe to get in to trying to get the egine out to change it with all the carbs and stuff needing disconnection...
  2. Zed

    Zed Gradually getting grumpier

    Maybe double check your belt if replacing or adjusting that was part of your service.
    Last edited: Apr 9, 2024
    Dave Goddard likes this.
  3. The belt is ok definitely not slipping...wish it was that simple.
    Zed likes this.
  4. Zed

    Zed Gradually getting grumpier

    OK before you serviced it? Step back though where you've been with you elbows?
    Dave Goddard likes this.
  5. I dont think its an elbow prob. It was running fine did the oil change last cranked it with ignition off to prime the oil lines, started it and all good, no ign light. Ran it for a while all good. Went for a drive, got about 5 miles then the light came on. I dont have a manual for testing the alternator in situ, i dont have an external regulator. I am guessing i may have a regulator prob, which i rwad may be built in to the alternator but dont know if it can be changed in situ or how to test it. Any pointers on whether this could be the case how to check and how to change...
  6. What voltage do you have with the engine running?

    An internal reg alt only has 2 wires.
    Is the smaller spade one secure?

    Some info here
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  7. mikedjames

    mikedjames Supporter

    There are brushes in the alternator that wear out.

    Usually this results in a flickering alternator light before it just stays on.

    Bad battery clamps (loose) and bad earth braided strap connections also cause issues with the alternator light coming on ..

    Modern aftermarket alternators e.g. 75A versions do not like a loose wire on the D+ warning light spade connector.. every time it breaks connection , the voltage regulator reboots; so if the wire shakes loose faster than once a second the alternator stays shut down. I had the connector just slightly loose and the light stayed on. Squeezed the female spade connector lightly with pliers, problem gone..
    Dave Goddard likes this.
  8. Hi all, i have had a chance to get out and do some more checks this evening. The alternator light was not exactly full on, it was pretty well full on but with a slight flicker in line with engine revs.

    I then took a 5w bulb and put it across the nutted connector to the spade connector. The dash alt light then went out. Weirdly i then took the bulb out of circuit and alt light went out straight away. I am guessing the alt light spade was dodgey or the bullet connector further down the line, so i swapped out the lot, made sure the alt connector spade was tight and all seems good. I guess it goes back to the start, where it was suggested i disturbed something in the service, that something being the lead that runs by the oil filler neck! Anyhow what a relief, massive thanks for you help everyone yet again!

    Incidentally anyone know what the max charge voltage you should see across the bat, engine running?
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  9. And one it easy to change the brushes alt in...presume its thro the black cap where the alt light connects? Sadly i dont appear to have the alt with easy access reg by the way. .
  10. Around 13.8V would be a good voltage.
  11. Thanks barry thats about what i have, so all good.
  12. mikedjames

    mikedjames Supporter

    On my 75A alternator, which has a modern IC regulator, if the "D+" wire disconnects briefly, the alternator goes into a startup sequence lasting about 1 second, with the warning light on. If the wire disconnects with vibration i.e. is a bit loose, the alternator light tends to stay on..
    On mine, giving the female spade connector on top of the alternator a squeeze with pliers to improve its grip fixed the symptom of the alternator light staying on too long..

    I see up to about 14.4 volts on my batteries when the battery voltage first rises up after starting. This should be somewhat dependent on the temperature of the alternator. When everything is hot, I think the voltage should be lower.
  13. So..the problem is back with the alternator, was going out immediately but now comes on a mostly stays on (pulsing high frequency) maybe it is the brushes. Are these changeable engine in on the alt i have which doesnt seem to have the large removable cover plate but does have a screwed on black plate type thing the alt light connects to.
    JamesLey likes this.
  14. mikedjames

    mikedjames Supporter

    The black plate with the three screws in it carries the brushes, and the wire for the warning light.
    It should unscrew and lift straight up.
  15. Hi mike, and all
    I took the brush set out and its fair to say the brushes are goosed barely anything left on them and one was kind of stuck up in the holder further than the other. Assuming its fair to assume this is the problem do you know where i can source replacements. I have looked but cant identify for sure the right ones. Enclosed pics of holder and brushes for ref..

    Attached Files:

  16. 77 Westy

    77 Westy Supporter

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  17. Thanks, thats a great help. I have spent ages trying to find somewhere that can supply them in the uk. I will try them tomorrow. Appreciate your help.
  18. mikedjames

    mikedjames Supporter

    The other alternative, if you cant source a numbers correct part is to measure the rectangular footprint of the brush e.g. and depth of brush holder guestimate how long the brush would be e.g. 4mmx7mmx19mm then ask for that size with a wire tail on it or look at pictures and descriptions on eBay. If they are too long its only a matter of moments with a file.
    But the Wood Auto site looks like it should deliver.
  19. Thanks Mike, i have two sets coming from wood auto for tomorrow. They were very helpful and only 10.00 delivered. I will give them a try and see what goes.
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  20. The good news is the brushes from woodauto were an exact match. I fitted them today and its fixed the alternator problem. Thank god i didnt need to get the engine out in the end. It was pretty easy to do so long as you have the lead length right and are careful in the space in the engine bay getting it back in.
    paradox, snotty, Dubs and 4 others like this.

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