She aint charging the batery

wackos00 · Padawan Joined: 05 Feb 2008 Posts: 53

Hey all,
bit stumped here. I was driving a long on Friday and I ran out of electricity! so I think my alternator is dead as my battery is only 1 month old, get specked home, Saturday morning phone the scrap yards they don't have a 2.2 legacy but they do have a 2.5 quad cam, (hanford hall if anyone is interested in it, didn't look at the engine much as all I wanted was the alternator) take my alternator along to check its the same and it is, so £40 done, take it home fit it, but still no luck, the alternator doesn't kick out a charge! Yesterday morning I take both alternators to a automotive electrical engineers and they bench test them, say both work but my old one the warning light doesn't work anymore.... Hmmm fit the 'new' one again double check everything and clean all my earths. Still no charging! Spoke to a friend of mine and he asked about my battery light on the dash board. It doesn't come on ever, put the key in turn it the light doesn't come on, oil light does but the battery one doesn't. Start her up and the light doesn't come on. He tells me to check the light bulb so I swap the battery and oil bulbs around and they both work. So am I right in saying the alternator needs to be excited to start charging, this is new to me so bear with me, and if so could it be a relay sticking/no working? or some wiring come undone somewhere?
Cheers,
Jack 95 EJ22 non turbo

ElusiveStranger · Posted: Thu Sep 03, 2009 2:04 pm Post subject:

Before you go any further, check that you have 12V (well battery voltage) on one side of the ALT light when the Ign's on
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wackos00 · Padawan Joined: 05 Feb 2008 Posts: 53

Ok so turn the ign to on, but don't start it, and see if I have 12V on either side of the alt light? because right now I doubt I will find any V there in that state. If there was 12v the light would come on wouldn't it? I havn't checked if I'm getting 12 v to the light when she is running but if I was wouldn't the warning light come on? I know the alternator should give 12v to to the alt light when running because the engineers told me it works, the old one doesn't. If the alternator has not been excited I wouldn't get 12v to the warning light would I? arrhhhh my brain hurts....

wackos00 · Padawan Joined: 05 Feb 2008 Posts: 53

http://www.forparts.com/techtips/subaru_ICsubaruelectricalsystem1105.asp
http://vwkd.co.uk/bb/viewtopic.php?t=1184&highlight=charging
these could be of help to me!

wackos00 · Padawan Joined: 05 Feb 2008 Posts: 53

Ok I'm still an idiot, did what elusive said and I was getting 12v both sides of the light in the on position and when she was running. So double checked and where I had joined the subaru alt light wire to the orignial vw one it had broken so 1 piece of chocky block later and all is good! why is it that when ever something brakes it takes me 3 days to figure it out??
Cheers,
Jack

ElusiveStranger · Posted: Thu Sep 03, 2009 8:06 pm Post subject:

Okey dokey.

You should only have 12V on one side of the lamp when Ign's on, Eng off. This is the 12v from the battery. The lamp lights as the "earth" is via the Alternator when it's not spinning.

Alt (0V) ---> Lamp ON <--- Batt (12V)

When you fire her up you should get a 12V from the alternator
so

Alt (12V) ---> Lamp OFF <--- Batt (12V)

Next question:
Has it run properly before?
{edit} read previous post! D'oh
_________________
The advice you receive on here is worth the paper it's written on.
Your experiences are worth shed loads to others, including the f'ups - live and learn.
Wouldn't YOU rather learn by someone else's mistakes? So would they.

'78 Bay, 2 litre 091 box, EJ20 NA & the ashtray's on the 'right' side.
I don't lean forward for hills any more Grin

Bugger, missed out on "Live fast, die young"

rjes · Posted: Fri Sep 04, 2009 1:14 pm Post subject:

Yes, The alternator does need power to it's field coils to charge. This is done differently on different spec Subaru alternators. Some use an ignition switched positive source to turn the field coils on, and others have a poermanant positive supply which must be turned on and off internally by the alternator itself. There are basically three types of alternator. The most obvious difference is the multi pin connector:

As your charging light bulb works, I'd suspect you are not getting power to the field coils for some reason. How it's wired depends on what alternator you have. The field coild are always connected via the multi pin plug:

1. Black round 4 pin = early - mid 1990's. Ignition switched field coils, yellow wire, fed via 15A 'ignition on' fuse in my harnesses. Also has a permanant positive supply to one of the terminals (white wire) in the 4 pin plug. Some also ECU control over the alternator output via a 4th wire (usually green) from the ECU
2. Grey rectangular 2 pin = mid - late 1990's. Permanant 12V positive to field coil circuit from battery via starter terminal - i.e. no ignition switched positive wire.
3. Light green oval 3 pin = 2000 onwards. Permanant 12V positive to field coil circuit from battery via the 10A fuse in my harnesses - i.e. no ignition switched positive wire. Some also ECU control over the alternator output via a 3rd wire from the ECU
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Richard,

R J Engineered Solutions
Quality Subaru Powered VW Components
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Gingernut · Wannabe Joined: 22 Sep 2009 Posts: 2

Hi Sorry for hijacking the thread but I have just realised I have the same problem...

The battery light never comes on and the alternator doesnt appear to be charging the battery.

I have 3 connections on the alternator. One is on the top which is bolted on and is a thick cable which goes to the battery without a fuse!! is that ok???

Then there is a connector to the left with 2 connections on it. The top one of the two has a thin jumper wire which goes to the top of the alternator providing a permanent positive.

The bottom one of the two goes towards the front of the van. (I'm assuming thats the light)

If I disconnect the bottom one and earth it, should the battery light come on?

Im wondering if the connections are round the wrond way. Does anyone know if this is wired up correctly?

Thanks, any help would be much appreciated.

Trevor

wackos00 · Padawan Joined: 05 Feb 2008 Posts: 53

Hi Trevor, if you could let us know what you are running ie engine and vehcal that would be helpfull, as for the thick wire with no fuse, that is correct, it should go from the alternator to the starter motor and on to the live side of the battery, if your doing any work with that one always best to disconect the earth from the battery.
Jack

Gingernut · Wannabe Joined: 22 Sep 2009 Posts: 2

Hi Appologies.

I have a bay window with a mid 1990's 2.2 subaru legacy conversion.

The live doesnt go via the starter it goes straight to the battery.

Hope that helps.

Trevor