Electricity Escaping

[MULLEY]

If you've taken a reading off the battery & its showing 11.5, Brian has said its knackered, so whilst the alternator is giving a full charge to the battery so its fine whilst on the move without having the main lights on, but as soon as you stop, the battery can't hold the charge (probably due to a duff cell) & thats why you have to jump start it & it appears fine when the engine is running. So its a knackered battery, or have i got my wires crossed?

[MULLEY]

I think you'll find the xantia alternator won't fit.It's a higher rated alternator with different fitments

Even if its the same xud 1.9 n/a engine as the BX? or do you mean the 1.9 turbo which may be what you're describing? or is it both, haha?

[rabbercelt]

have you got or could you borrow a known decent battery and check what happens to that before spending?

[Mothman]

As i dont have a meter to read this, i took my motor to a local garage who put a meter across the batt with the engine running and only got a figure of just under 12 volts. As this isnt enough to power everything and charge the batt, alternator therefore buggered. New alternator[twice cos the first was also buggered too] cured the problem.
How old is both the battery and the alternator? Ime sure its one or the other or could be both. Garage told me that the alternator should be bunging out at least 14v to be doing its job properly.

Andy

[rabbercelt]

I think you'll find the xantia alternator won't fit.It's a higher rated alternator with different fitments

Even if its the same xud 1.9 n/a engine as the BX? or do you mean the 1.9 turbo which may be what you're describing? or is it both, haha?

I take your point-I was specifically thinking of the 1.9 turbo .

[Defender110]

If your alternator is charging it should raed at least 13v (low charge) across your battery when running and a minimum of 13.5 v for a health alternator. If it is only reading 11.5 volt across the battery when running then the alternator isn't chatging.

EDIT: As Andy has also said.

[mat_fenwick]

/\ WHS. Definitely charging system. Just a thought, I've always read (in relation to pre 80s vehicles) that if the charging warning light bulb as blown then it prevents the alternator from charging. IIRC this was something we discussed recently(ish) and I can't remember whether this still hold true in relation to the BX. However, if the lamp lights when you turn the ignition on but don't crank, it's obviously OK so ignore my suggestion!

[vulgalour]

Tomorrow I'll get out and check fuses and bulbs and whatnot before condemning the alternator and/or battery. I'm hoping for a cheaper fix so I can just get on with driving this thing.

[MULLEY]

Just to clarify, if the alternator was working fine & you put the meter on a duff battery, it would still read 13.5v?

[mat_fenwick]

Pretty much. A dead short inside the battery, would drag down the output voltage of the alternator to some extent, but not to 11.5 V when we know the battery is capable of starting the engine when put on charge.

[MULLEY]

If therefore as you guy's are suggesting that its deffo the alternator thats duff, that should get the red charging warning light on then, must be a bulb thats out?

[electrokid]

when we know the battery is capable of starting the engine when put on charge.

And that's the crux of the matter - and how we know that the alternator isn't charging. So if you've checked all the connections to the alternator then you're going to need one of these...

http://www.ebay.co.uk/itm/190667118300? ... 564wt_1056

It says it's 110 amp output - I don't believe that but check with the seller first.

If therefore as you guy's are suggesting that its deffo the alternator thats duff, that should get the red charging warning light on then, must be a bulb thats out?

Could be...

Just a thought, I've always read (in relation to pre 80s vehicles) that if the charging warning light bulb as blown then it prevents the alternator from charging. IIRC this was something we discussed recently(ish) and I can't remember whether this still hold true in relation to the BX. However, if the lamp lights when you turn the ignition on but don't crank, it's obviously OK so ignore my suggestion!

The little connection on the alternator is just connected to the bulb - that's all it does these days (it used to drive the field coil and control the alternator output but the regulation is built-in to the alternator now). The bulb may indeed be duff - but it could also be another fault in the alternator itself - we'll only know when you have a working alternator in there and made sure the small connector is actually connected.

If you measure the battery while it's being charged the voltage should rise from 11.6v for a flat battery to around 14v for fully charged. When you disconnect the charger from a fully charged battery then the voltage may drop as low as 13v.

If the battery is 'wearing out' then its internal resistance will be higher than normal - this is most easily spotted when being charged from a mains charger - the charge current will be lower than normal and the battery voltage will rise more quickly and be higher than normal at the end of charge - up to 15 volts (with the charger still connected and running).

Meters are really cheap these days so there's no reason not to have one. Some time ago I bought 10 of these...

http://www.ebay.co.uk/itm/DIGITAL-MULTI ... 256cad5ea5

because the price drops at 10 off and there are times when I need to measure several things at once. (I bought them from CPC but I have bought other stuff on eBay from babz are they are fine.)

I've also bought some of these...

http://www.ebay.co.uk/itm/330792996991? ... 2951wt_886

for another type of project - but you could fit one permanently if you wanted to so you could keep an eye on the battey volts. This class of meter only measures positive volts - black wire is ground, red wire is power for the meter and the yellow is connected to the voltage you want to measure - in the car connect black to chassis and connect the red and yellow wires together to 'ignition' 12v feed - it's perfectly happy to measure the supply it's actually using for power. They are not super accurate but they are good enough for the purpose - the biggest error I've seen on these 4 digit ones has been 0.03 volts. (The 3 digit ones can be out by 0.3 volts which is not so good.)

If you buy from overseas on eBay remember that anything over £15 in value now attracts VAT (anything over £18 attracts duty as well) and if it's over £15 it has to go through the post office facility for dealing with the extra charges - that will cost you an extra £8 on top. If you buy at the moment it will take slightly longer than usual - it's the Chinese New Year - I don't think they get pissed or anything - but they do close the post office

[Mickey taker]

Take battery to any good motor factor or halfords and get them to check it first, may be a dead cell or two , I say this because a battery is easier to remove than an alternator and if the batterys good you can tick that off your list

[kiwi]

If therefore as you guy's are suggesting that its deffo the alternator thats duff, that should get the red charging warning light on then, must be a bulb thats out?

Not all the time!

I thought that until the TXD showed some strange flickering to the headlights. Ignored it until the battery went dead one time a little gizmo picked up in the auto store showed the Alternator had an intermittant fault this never showed on the dashboard. Corroded connection in the wiring loom towards the battery being cleaned helped. Although issue is still there another candidate could be battery terminals.

The dash light (if working at ignition) does not always light up for a fault.

[Defender110]

Take battery to any good motor factor or halfords and get them to check it first, may be a dead cell or two , I say this because a battery is easier to remove than an alternator and if the batterys good you can tick that off your list

But there is no charge voltage! When you measure the voltage across the battery you are basically directly measuring your alternator output, the fact the reading is 11.5 volts WHEN RUNNING means the alternator is not giving out any charge voltage; the 11.5volts reading is just the flat battery output. The probe on the battery positive is basically the same as putting the probe directly to the back of the alternator output. The battery could be a duffer but there is definitley no charge output reaching the battery, putting a new fully charged battery would work for a day and then it would be flat again because there is no charge going into the battery circuit to recharge it. He now needs to check why there is no charge output which is either and usually the alternator itself or the connector plugs / wiring from the alternator.