Strange electrical problem leading to drain.

[daz_sri140]

I have a 98 vectra sri, and im having a very strange problem.

My battery kept going flat so i replaced the battery, all seemed fine for a day or two, but tonight im experiencing problems. i have left it running on the drive whilst i washed the car, then all of a suddun the T/Control light came on, then the abs, then the instrument panel went off - at this point i turnt the engine off, and it failed to restart, i tried a few times but the battery was completelty dead.

I went out to the car 30 mins later to put the battery on charge, but i thought i would see if it started and it fired up instantly as if all was fine, but then the lights all came on again and it all happened again.

Im unsure where to start, im not getting a warning light on to indicate the altenator. The car is just a run around, so im reluctant to throw money on things that may not be at fault so i have turnt to you guys for some advice

Thank you

[Tom Williams]

Sounds like an alternator failure to me. Its not charging the battery.

[daz_sri140]

See now thats what i thought, but then if this was the case would the battery light not come on? and what would allow it to restart after 15 mins or so?

Is there any way of testing the altenator?

[ayresyy]

easy way is just stick a volt meter on the battery posts with the engine running, you should get between 13 and 14 volts if the alternator is working, if its less theres a good chance it's dead.

[daz_sri140]

Cheers, so basically the battery should be about 12v when engine is off, and 13/14 when running, anything less would point to an altenator problem.

Is there anything else that could cause this kind of drain?

Thanks for the advice

[daz_sri140]

Right just been out to the car and its showing 11.8 when engine is off and 11.4 when engine is running. I think you guys hit the nail on the head

Next question is where to get a new altenator from? am i better off getting new or could i get one from a breakers?

Cheers

[MSG]

diodes inside the alternator may have gone leaky or short circuit and will drain the battery, when gone wrong it doesn't always bring on the fault (charging light).

but make sure that the charging light comes on when you turn your ignition on first, if it doesn't then your altinator won't charge even if the alternator is new, it doesn't charge unless the charging light bulb is working.

Also a good or a new battery will recover slightly enough to restart a car if left for a few minutes, so that is not unusual phnomenon.

[MSG]

you could get a recon alternator from your local alternator repairere, check your local directory. Should get one exchanged from £30.00 - £45.00 with about 3 to 6 months warranty.

[daz_sri140]

A ha, well i have just been out to check as i dont recall seeing a battery light on before, and it doesnt come on with the ignition.

along the right hand side, with ignition on i get the oil light, abs light, a space and then the TC light another space and the air bag. Along the other side i have the engine light and the parking light.

Has this opened a whole can of worms?

cheers

[james sport]

Originally Posted by daz_sri140

Has this opened a whole can of worms?

cheers

no, change the bulb and hopefully that should cure the problem - the bulb provides the excitation current to the alternator.

[Orbital]

Originally Posted by james sport

no, change the bulb and hopefully that should cure the problem - the bulb provides the excitation current to the alternator.

not got the bulp on my dash conected but all i need to do to get it to charge is rev it to about 2500rpm and starts charging

since all your tests have been in the drive did you rev it up at all or just leave it idle?

[james sport]

Originally Posted by Orbital

all i need to do to get it to charge is rev it to about 2500rpm and starts charging

yes that can happen from the residule magnetism left in the rotor, once a small current is generated this is self sustaining and the alternator will then work normaly (other than the warning light not functioning) but it is not really a fix, you do really need to check/replace the bulb.

[Orbital]

on mine it's more than just the bulb the wire managed to short itself out and fry most of my cars wiring loom. i'll redo it soon when I have enogh time if anything goes wrong redone all the rest just not that one.

[MSG]

yes strictly speaking the bulb is essential, for normal alternator operation, you should not rely on residual magnetic field in the rotor, again depending on the strength of residual magnetic field left over from last excitation, if this field becomes weaker then your alternator may require extremely high engine rpm to kick it into action, not necessarily 2500rpm, it may be so weak that the alternator may have to be spun at over 5000 RPM sometimes (+10,000RPM Alternator speed)

[daz_sri140]

Cheers MSG im going to have a look into this after work, im also going to ensure all the wires on the back of the altenator are tight and clean.

Appreciate your advice

[Jack]

Agreed, before you start looking for an alternator, get the bulb changed.

[Galahad]

And also put your location in so if you do need an alternater, chances are someone won't live far away and can sell you a good second hand one.

[ST_Boy]

Guys...

My mum has a 2.2 Astra. I've replaced the battery but within a couple of days it dies. I've checked the voltage of the alternator and shortly after starting the engine it peaks at 13.2v then slowly drops down to 12.1v and even 11.9 at times. I guess the alty is fried.

This lamp you speak of, is it the little "battery" icon on the dash?

[Fow16v]

yea thats the one, should light up when you switch the ignition on

[ST_Boy]

Ah right, well that lights up fine. What is the purpose of the alternator lamp then, if the battery one is the most obvious indicator of a faulty alternator?

Also, anyone know of a good place to buy a second-hand / cheap alternator for a 2.2 Astra petrol around Southampton area + anywhere to fit it ?

Thanks in advance

[Astra Dan]

The battery light and alternator light is the same thing. It's used to give the alternator a 'kick' to start it charging and can illiustrate a fault in 2 ways (i.e it not coming on with the ignition and it not going off with the engine running).