need new alternator?

[mattspear]

Well yesterday the car would not start, thought flat battery but had no leads to jump start it, so green flag came and charged the battery and it fired straight up, put a multimeter on the battery with the engine running and it was reading anywhere from 11.4 to 13.0v so I'm thinking alternator needs changing, any other ideas?

[Ben50n]

If it didnt start it may be the battery that has had it. A fully charged battery should read over 12.6 volts, I would get the battery load tested, they can read the correct voltage but do not give the amperage.

[mattspear]

Reckon its worth changing the battery first? Pretty sure its the original gm one, is there an upgrade part do you know? Thanks for your response

[Handyandy-UK]

I'm with Ben50n on this.... you'd be far better off having a load test done first to determine the battery condition, rather than taking a guess and just changing it. Many battery places (Hi-Q, etc) will test it for free.

From my perspective, with the info you have given so far I would say there's more chance the alternator is at fualt than the battery - with the engine running, put as many lights, radio, hazards, etc on as you can and then measure the voltage at the battery - a good alternator should be putting out a pretty steady 14-14.5v under load.

[mattspear]

Just did what you suggested Handyandy-UK and it's only reading a maximum of 12.0 but it constantly changes down to as low as 10.9v should I see a steady reading if all was well? Might check the Beemer see what that does, thanks for your help, bought a diesel to save me some fuel money but seems to be a nightmare atm, glad I got a warranty

[Handyandy-UK]

Yep sounds like the alternator is struggling to put out enough charge so my money's on the alternator being a gonner. A good alternator should be able to cope with all the electrical load of the vehicle to which it is fitted and so if it's putting out only 10-12v under load I would guess the regulator is dying.

Downside is if it's been doing this for a while, there is a chance the battery MIGHT have suffered too.

If it were me I would get an exchange alternator sorted and in the meantime get the battery on charge. As far as a warranty goes I wouldn't hold out a lot of hope - many don't cover items considered to be 'failed due to being at the expected end of their life'.

[GT3071R]

Autovaux in harrold hill Essex. Good price for alternator and mail order

[Bigtee]

I think there is 2x options here been one that gives out more amps go for that one, brighter lights, stronger battery.

[mattspear]

Well car needs new alternator and a new battery, waiting to hear back from warranty company (wms group) with the go ahead, if they won't pay out for the battery as I doubt they will what grounds do I have seeing as I only bought the car 4 weeks ago from a dealer? Thanks

[DAVIDD88]

Is the battery deffo needing changed as its proberly just flat as alternator stopped charging tbh