Alternator problem, help needed!

[t111bul]

Hi guys

I have a 90 spec 16v that the battery keeps going flat on. I have a battery/alternator tester that keeps saying the car is charging ok until i turn on the electrics. I have tired three alternators and they all give the same results, they arn't new but the 3rd one came of tried and tested car. Does any one know what might be wrong?

Tim

[JC]

how much is the battery reading ( volts )  across the terminals at the follwoing times

1, engine off

2, engine running without much load

3, engine running with load ( lights, heater, rear window etc )

[Organisys]

...and check all your earth connections carefully.

[t111bul]

Hi,

My battery charger says the battery is 12.6 volts but i haven't checked the voltage when running and then with electrics on as my tester just comes up with lights to tell you the state of charge and alternator state. I'll try and find my volt meter to test the voltage and i'll clean all my earth points up and see if that helps.

[JC]

yep, need to see wot volts its kicking out when the engine running before we can move on 

[t111bul]

I've just been out in the cold checking my battery, The battery without the car running is 12.2 volts, with the car running it's 13.8 volts and with all the electrical stuff turned on it's 11.8 volts at idle and with 2000ish rev's its 13.2 volts. I would of thought this sounds about right?

[JC]

yep, sounds about right,

so its charging ok,

so either the battery is goosed ( how come i wasnt flat when you went out to it today ? )

or you got summat draining it, alarm, boot interior light or summat ?

[danny_p]

battery hate the cold  if they are weack  a cold morning will knock them out till it warms up, when this happens theres only a few week left in them anyway tho 

[t111bul]

I work away so the car does get left for a couple of weeks at a time, i charged the battery up two weeks ago and left it disconnected so it hasn't gone flat. The car only has an led for the imobiliser so it must be that thats making it go flat! At least the car is ok to use now.

[t111bul]

Oh and the battery is the second new one in 3 months so it should be ok and the car is kept in a garage so it doesn't get that cold.