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Vauxhall Astra - battery/alternator issue

Hi folks
Hope you can help
Vauxhall Astra (2007) 1.9
Bought a call from dealership not long ago, car required a jump start, drove it two hours home, checked it 6 hours later and engine won’t start.
Battery light now on dash
Last serviced may 19 with prev owner (change of fuel filter back then)

Is this more likely a need of battery change than issue with alternator?

Seems as if the journey home charges the battery but then goes dead after few hours as not charging when turned off…

Thanks in advance

Check the obvious…are the battery connections tight and clean? how old is the battery?there should be a date of manufacture on the battery case.Make sure that all lights are turned off when leaving your car…a simple dome light left on will drain your battery in just a couple of hours.Since replacing an alternator can be difficult and expensive on some cars, I suggest you have the entire charging system tested before doing so.

If the charge light is illuminated on the dash it will be your alternator… During the time the light was off…the alternator was working and most likely trying to charge a stone dead battery with internal damage to its plates etc… The alternator will continue to try and try to charge that dead battery (which is very tough on the alternator btw) until it simply fries the alternator, usually brushes, but any failure will do…and will arrive in short order.

Never ask an alternator to charge a deeply discharged battery, let alone a battery that will not ever accept those electrons willingly… It will kill any alternator in the process. The alternators job is to maintain a state of full charge in the battery…it is not supposed to charge batteries from their lowest voltage level repeatedly (sure this happens at times and alternators live through it) but if you asked the alternator it would tell you that it did not enjoy all that work…and that it is tired and hot to the touch… Use a battery charger to bring the batt to full charge and the alt will be happy to keep it there for you…it does not wish to do both.

Now you will need a new batt…and an alternator.


When you ask an alternator to recharge a discharged battery, it can fry the diodes in the alternator.

If diodes fry, it can draw current from the battery as the vehicle sits.

This is why every alternator I install includes this warning.


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Got a computer file for that document @Tester ? I could benefit from printing a bunch of those out.

If not… I’m an excellent forger… I mean, a guy I know could probably copy to some some extent.