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  • FIRST POST
    • Freddybob
    • By Freddybob 5th Mar 18, 12:49 AM
    • 3Posts
    • 0Thanks
    Freddybob
    Need new alternator?
    • #1
    • 5th Mar 18, 12:49 AM
    Need new alternator? 5th Mar 18 at 12:49 AM
    Hi,

    The red battery warning light came on on my dashboard when I turned my car (2006 Peugeot 107) on a couple of days ago. I managed to drive it back home ok, then left it for a couple of days before trying to fix it as I've been busy. As of yesterday the battery had gone flat and I couldn't start the car at all.

    Last night I took the battery out completely, gave all the surfaces and electrodes a clean with sodium bicarbonate, and charged it with a battery charger. However this morning I still couldn't turn over the engine so I called the AA - the mechanic managed to turn the car back on and the battery light was no longer on.

    However the mechanic said that since the battery light had come on, the car's alternator must need replacing. He tested it with a voltometer and it was above 14 the whole time which apparently meant it was working at the time, but he reckons it's definitely going to die on me again.

    I've looked around and this looks like a relatively expensive repair, which obviously I'd rather not undertake if I don't have to (especially as a skint student)!

    Essentially my question is whether a single instance of the battery light coming on means that the alternator definitely needs replacing?

    Cheers
Page 1
    • Sam Fallow
    • By Sam Fallow 5th Mar 18, 1:48 AM
    • 843 Posts
    • 1,938 Thanks
    Sam Fallow
    • #2
    • 5th Mar 18, 1:48 AM
    • #2
    • 5th Mar 18, 1:48 AM
    If it is reading over 14 volts whle running then that points to a good alternator. If you charged your battery and it still wouldn't start but did when the recovery jumped it, then it sounds like a failing battery.

    Any cold period of weather can see off a poor battery.

    If money is tight then try a scrap yard for a cheap replacement.
    I don't like morning people. Or mornings. Or people.
    • parking_question_chap
    • By parking_question_chap 5th Mar 18, 7:20 AM
    • 1,612 Posts
    • 1,401 Thanks
    parking_question_chap
    • #3
    • 5th Mar 18, 7:20 AM
    • #3
    • 5th Mar 18, 7:20 AM
    How old is the battery?
    • arcon5
    • By arcon5 5th Mar 18, 8:27 AM
    • 13,533 Posts
    • 8,596 Thanks
    arcon5
    • #4
    • 5th Mar 18, 8:27 AM
    • #4
    • 5th Mar 18, 8:27 AM
    Did he load test the battery?
    • AdrianC
    • By AdrianC 5th Mar 18, 8:32 AM
    • 17,362 Posts
    • 15,701 Thanks
    AdrianC
    • #5
    • 5th Mar 18, 8:32 AM
    • #5
    • 5th Mar 18, 8:32 AM
    The "battery light" doesn't tell you anything about the battery. It's a charge light, and it tells you that the charge voltage is not what it should be. The alternator generates charge, the battery stores it.

    If you charged the battery last night, and the car won't start this morning, then the problem is the battery. ASSUMING the failure to start is due to a shortage of electrickery (dash lights on with key to normal run position, dim or off and whuuuurrr-whurr or simply click with key to starter position)

    A dying alternator may well have taken the battery with it.

    VERY basic diagnosis will tell you what's what. Plug one of these into the ciggy socket - https://www.ebay.co.uk/itm/391918395276
    Anything lower than 14v when the engine's running? Alternator.
    Charging OK, but anything lower than 12.5v with the engine off? Battery.

    A decent-brand battery should be 50 or so for a 107 (size 002L), and an alternator is 75 plus an hour or so for fitting.
    http://www.mister-auto.co.uk/en/alternator/valeo-436489_g4_a021436489.html
    Last edited by AdrianC; 05-03-2018 at 8:36 AM.
    • Freddybob
    • By Freddybob 5th Mar 18, 9:11 AM
    • 3 Posts
    • 0 Thanks
    Freddybob
    • #6
    • 5th Mar 18, 9:11 AM
    • #6
    • 5th Mar 18, 9:11 AM
    Thanks all for your replies.

    The mechanic did do the test with the voltometer and it ran above 14V the entire time - does this reliably rule out problems with the alternator? I have a trip from Leeds to Southport planned this weekend and as you can understand I!!!8217;m now feeling a little nervous about that, but equally don;t wanna waste money to repair a perfectly good alternator!
    Last edited by Freddybob; 05-03-2018 at 9:22 AM.
    • Raxiel
    • By Raxiel 5th Mar 18, 10:52 AM
    • 655 Posts
    • 357 Thanks
    Raxiel
    • #7
    • 5th Mar 18, 10:52 AM
    • #7
    • 5th Mar 18, 10:52 AM
    Could the belt have been slipping?
    • arcon5
    • By arcon5 5th Mar 18, 10:57 AM
    • 13,533 Posts
    • 8,596 Thanks
    arcon5
    • #8
    • 5th Mar 18, 10:57 AM
    • #8
    • 5th Mar 18, 10:57 AM
    Thanks all for your replies.

    The mechanic did do the test with the voltometer and it ran above 14V the entire time - does this reliably rule out problems with the alternator? I have a trip from Leeds to Southport planned this weekend and as you can understand I!!!8217;m now feeling a little nervous about that, but equally don;t wanna waste money to repair a perfectly good alternator!
    Originally posted by Freddybob
    Sort of. He could have also done a amperage check but personally I think your battery knackered.. If fully charged it could be the voltage is dropping too much on cranking. A battery load test can check this.

    If it starts I'd take it to a garage and ask them to do a battery check. Even the nationals can't get this wrong. The testers are something any workshop will have
    • Freddybob
    • By Freddybob 5th Mar 18, 11:59 AM
    • 3 Posts
    • 0 Thanks
    Freddybob
    • #9
    • 5th Mar 18, 11:59 AM
    • #9
    • 5th Mar 18, 11:59 AM
    Raxiel - I hope not, the belt was only changed in December! Looks ok to me although I'm not a mechanic

    Arcon - thanks for the tip, I've booked into Halfords for a free battery check tomorrow, will see what they have to say!
    • Raxiel
    • By Raxiel 5th Mar 18, 1:58 PM
    • 655 Posts
    • 357 Thanks
    Raxiel
    Raxiel - I hope not, the belt was only changed in December! Looks ok to me although I'm not a mechanic

    Arcon - thanks for the tip, I've booked into Halfords for a free battery check tomorrow, will see what they have to say!
    Originally posted by Freddybob
    I'd expect it to squeal if it was loose, but a new belt makes it more suspect to me. A brand new belt may need the tension re-adjusting after its been run for a while. If there were a lot of electrics on (particularly things like screen and seat heaters) the extra load on the alternator may have made it more inclined to slip.

    It's possible there isn't one single fault, and a combination of things just happened to come together in the cold weather to create a more obvious issue.

    Just a thought.
    • thescouselander
    • By thescouselander 5th Mar 18, 4:44 PM
    • 5,379 Posts
    • 4,999 Thanks
    thescouselander
    Could be the brushes on the alternator. If they're wearing out you might well get a good voltage reading under no load but it will drop under large loads such as when the rear demister is on.

    Might be best to get an auto electrician to look at it. If it is the brushes these can usually be replaced at relatively low cost.
    • EdGasketTheSecond
    • By EdGasketTheSecond 5th Mar 18, 8:28 PM
    • 550 Posts
    • 303 Thanks
    EdGasketTheSecond
    If it is the brushes these can usually be replaced at relatively low cost.
    Originally posted by thescouselander
    About 30 years ago yes; not any more sadly in most cases.
    • Robisere
    • By Robisere 5th Mar 18, 8:48 PM
    • 2,240 Posts
    • 3,052 Thanks
    Robisere
    I suspect the battery, not the alternator. Please do not go to an auto-electrician: they are expensive, it is a specialised part of the motor trade and charges accordingly. If you have a nearby independent garage that you can trust on recommendation from friends or family, go there. Ask them to check battery and alternator. If they agree upon battery, ask how much they charge to supply and fit. Independents usually have deals from Motor Factors.

    If it is the alternator, same applies: ask how much for supply and fit, they will be able to supply a pattern or remanufactured Motor Factor alternator. Whatever happens, always ask for warranty details and a receipt, preferably on headed paper.
    Last edited by Robisere; 05-03-2018 at 8:56 PM.
    I think this job really needs
    a much bigger hammer.
    • thescouselander
    • By thescouselander 5th Mar 18, 8:59 PM
    • 5,379 Posts
    • 4,999 Thanks
    thescouselander
    About 30 years ago yes; not any more sadly in most cases.
    Originally posted by EdGasketTheSecond
    It can still be done. I guess it might be a bit more involved these days which is probably why a lot of garages will just swap the whole unit as they don't want to spend the time on it. For the DIY mechanic it's still a viable and cost effective repair
    • EdGasketTheSecond
    • By EdGasketTheSecond 5th Mar 18, 10:22 PM
    • 550 Posts
    • 303 Thanks
    EdGasketTheSecond
    Some units you just can't get to the brushes; and the brushes aren't available if you could.
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