Battery or alternator?

[Judderi]

Ok when driving home last night my battery light was on. I almost got home but my lights went off then the engine died through lack of power. Is this more likely to be the alternator or the battery? It will jump start off another car but as soon as you remove the jump leads it starts to die again.

[Whittle55]

Sounds like the battery to me.

[gibby]

I always thought that if your battery light stays on while the car is running then your battery is not charging so it's a buggered alternator?

[Gambit]

i would suggest altertnator failure!! the alternator would need to be not charging at all for the light to come then for the lights to go out then the car die!

i was able to drive around for months with my battery light on. it was just the voltage regulator in mine which meant it was giving a constant charge!

might just be something as simple as loose connections between alternator and battery

[Whittle55]

Best bet to go and get them checked out first.

Reading the thread again the alternator may be the most likley. When diving haome at night you will have everything pulling of the poor old battery.

Gibbys right though check connections may well just have a loose one.

Andy.

[Judderi]

Yeah i had a check of the power lines from the alternator to the starter and battery plus the earth strap and all seem ok. Me thinks it the alternator. Thanks guys

[LPG'd Oakie]

I had this going down the M40 once....I would say It was your alternator too!

[Chris Green]

Fit another batthery (Try and borrow one, just in case your old one just needed charging).

Then check the voltage accross your battery (With a voltmeter) once the car is running. It should read 13.5v to 14.5v.

If it is less than that, it means that your alternator is not charging your battery, and that is the problem.

If this is the case, your battery will probably be fine, but it will need charging (with a mains charger). This is because the alternator cannot charge a completely flat battery.

Sorry if I'm teaching you to suck eggs....

HTH,

Chris

[Tucker]

Mine was the smae last week, wasa doin a 180 mile trip and 30 into it the light came on was fine drivin but a day or two later would not start, i striped down the alt and checked all the wires, put her back on and still the same. (light on and would not start) so took it all back off and tried to get service bits like new bushes but no joy. Cafco wanted 130 notes and GSF wanted 70, got the higher amped one too

Job done

[Chris Green]

You could take the old alternator to a local auto electrician place, and they should test it for you. (They usually do it for free, because they think they will be able to sell you a new one!).

It could be that it was just the regulator or rectifier that is knackered. A regulator is typically about ?15. (Not sure for a VW one though).

Its worth keeping as a spare then.

That's assuming you didn't throw it away!