R25 alternator electrics
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Thread: R25 alternator electrics

  1. #1
    don
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    Icon8 R25 alternator electrics

    Hi all
    I have a problem with the electrics attached to my R25s alternator.

    The battery has been going flat if I leave it more than 3 days and there is a high pitched electrical noise coming from the area of the alternator. I have had the unit checked and it is fine so something attached via that wiring must be the culprit. There is definitely a load on the battery with the ignition switched off as I am getting a small spark when I disconnect the positive terminal. And its more current than just the clock would use.

    The Bosch alternator is the original fitted to the car as the loom has not been tampered with and all the connection fittings are there as they should be.

    The computer and ignition system are also on that side so Im not sure where to look next.
    Any help would be appreciated or its off to the auto lecs.R25 alternator electrics-20150122_192622.jpg

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    I would suggest removing wires, one at a time, and each time, and each time checking if the current draw has stopped.
    Start with the wires on the alternator - I realise you said it had been checked, but discharge through one of its diodes is normally a potential cause of such a problem. After the alternator, then go through the fuse box pulling them out one by one.

    If you dont have a multimeter, perhaps buying one would be good so you dont have to just look for a spark at the loose battery terminal. Bunnings sell cheapies for $10 so it need not be an expensive purchase! Darn handy things to have around too. All that said most likely you have one so pardon me if I am preaching to the converted.

    Cheerio
    Edward.
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    1000+ Posts Haakon's Avatar
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    Bosch is not the original fitment - Valeo is. That relay you've pictured is also not original - looks like someone has fitted a generic Bosch with an external regulator.

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    COL
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    Hi Don

    I second the disconnecting the alternator and seeing if you have a spark as you do when you disconnect the battery.

    Another way if you want to save purchasing an multimeter (even though they are very useful and a worth while investment) is to pull all the fuses see if the spark still exists, if not start replacing the fuses one by one and after each fuse is replace connect the battery to see if the spark is there. If so then the last fuse replaced is your problem circuit.

    Give these suggestions of mine and Elpicador a go and report back with what you find.
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    Regards Col

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    The old boot light is the normal culprit

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    I second the disconnecting the alternator and seeing if you have a spark as you do when you disconnect the battery.
    The <spark> test is pretty primitive. A 12 volt test lamp is a better alternative (5 watt 12 volt globe) and often is a satisfactory alternative to a multi meter.

    If the alternator is whistling I would supect the sense terminal is not being disconnected when ignition is off. Check the relay onthe firewall is not faulty.

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    don
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    many thanks everyone Im thinking that perhaps the sense wire is the problem or maybe a duplication.
    On the B+ terminal I have the charge wire a red and white wire then I have the Lamp wire and sense wire terminal on the back of the internal regulator connector.
    so ill get the trusty voltmeter out and go to work on the circuit.

    The alternator is a bastard to take off as its under the inlet manifold so ill just have to fiddle my way through

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    Quote Originally Posted by don View Post
    many thanks everyone Im thinking that perhaps the sense wire is the problem or maybe a duplication.
    On the B+ terminal I have the charge wire a red and white wire then I have the Lamp wire and sense wire terminal on the back of the internal regulator connector.
    so ill get the trusty voltmeter out and go to work on the circuit.

    The alternator is a bastard to take off as its under the inlet manifold so ill just have to fiddle my way through
    Try pulling the relay from the socket and seeing if the noise stops. If it does problem found without removing the alternator.

    If it's been working 100% prior, I'd suspect the relay is jammed closed or the col permanently power by a wiring fault.

    The relay should only be powered and thus the <s> terminal connected to the battery when the ignition is on.

    I'm guessing it's a Bosch Alternator off a Holden v* series. There are a very suitable 80 amp machine for transplants,

    As my 504 TI attests.

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    don
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    I think you are right some_one the everything on the web points to a holden implant. pulling the relay out didn't make any difference but it shouldn't need be there for a sense circuit anyway. The problem has always been there Im thinking since I was gifted the car but I don't drive it a lot so now the problem is evident.

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    Hi Don,
    As you know I live close to you and would be happy to lend my experience if you like.
    However I am away till the weekend so it would be after that some time. PM me if you want too !
    Jaahn

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    Most modern Bosch alternators have a 1 wire connection (a simple 12V+ field activation wire that turns on with the ignition) no relay or other stuff required (2 wires if you include the big current cable...)

    The regulator and brush holder are a common unit (quite cheap and easy to replace -held in by two screws/bolts...often in situ)

    When they fail, the often go into an overcharge situation and boil the battery causing damage. As has been stated, a volt meter is your friend and if placed in parallel on the battery terminals shouldn't really read much past 14V with the alternator charging (at around 2000rpm).

    It may also be that the battery may not be holding charge because it is stuffed (perhaps due to overcharging). A simple load test should let you know if it is.

    If your battery is ok but losing charge with everything off, just pull a terminal and connect an amp meter in series and see how much current is being drawn. Leave it connected and just pull fuses to pinpoint the circuit(s) involved.

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    pulling the relay out didn't make any difference but it shouldn't need be there for a sense circuit anyway
    That simply shows that the relay is incorectly wired or not part of the alternator circuit.

    Make no mistake, if it's a holden alternator it needs a relay (or transistor) to disconnect the sense terminal or it will whistle (the dc to dc converter internal to the alternator) and draw current from the battery as soon as the alternator stops rotating.


    gererator to alternator conversion.......

    Post 4, in the thread above has a wiring diagram in pdf format.

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    don
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    Well you are right on the money because it whistles its head off so Ill pick up another relay

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    Quote Originally Posted by don View Post
    Well you are right on the money because it whistles its head off so Ill pick up another relay
    Relays are reliable devices.

    If the noise doesn't stop if the relay is unplugged, it unlikely to be at fault. If it's correctly wired unplugging the relay from the socket must disconnect the "s" circuit from the battery.

    I'd be checking the circuit wiring thoroughly to ensure the alternator is correctly wiredbefore going any further.

    Incorrect wiring of the voltage sense circuit can cause the alternator voltage to go sky high and boil/ explode the battery and fry ecus et al. Be careful!

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