Help! Battery or Alternator? - angiet
Around 2 months ago my car (Astra 1.4Lsi 1992) failed to start. The mechanic tested it to find that the alternator wasn't functioning. So we replaced it and it was then running fine. Two days ago the same thing happend, again we had it tested to find this time it was the battery and again this was replaced. We then took the car for a run and with lights, wipers and fan on found the battery to be draining yet again? Does anyone have any suggestions? Did we need a battery? Did we need an alternator? What can we try next? cos we don't have a clue!!!
We would apreciate any ideas.

Help! Battery or Alternator? - Vaughan
Hello there. It is clear that you have a current drain somewhere. Get a garage to test the voltage at the battery; you should be recording an optimum voltage of between 12.5 and 14.8 volts. However, you should also test the resistance at the alternator itself - it is possible it has an internal short which is causing the drain.

There's quite a good little guide here:

Although it's for SAABs, the basics are essentially the same.

Help! Battery or Alternator? - Aprilia
Get a cheap digital multimeter (DMM) - you can get them for less than £5.
Connect across battery and start engine. Switch on headlights. Battery should read around 12.5V.
Now rev the engine to 2000-3000rpm. Voltage should rise to around 13.6V, or a little more. Headlights will glow a lttle brighter.
Any less than 13V (or more than 14.5V) and you have an alternator problem.
Help! Battery or Alternator? - gemma
buy a haynes manual and it will lead you by the hand thru the tests to determine whether batt or alt. good luck
ps also you will need a multimeter [no need to spend a fortune].
Help! Battery or Alternator? - David Davies
Make sure you have a good clean contact between the alternator and the engine block via the dedicated earth wire which runs from the adjustment bracket for the alternator and the cylinder head.Clean to bright metal and use a new alternator adjuster bolt.This often rusts and causes poor charging.
David Davies (Tune-Up Raglan)
Help! Battery or Alternator? - AndyT
I can second what David D says about the short earth link. I was investigating the same symptons on an Astra some years ago, the charging light would go out but it wasn't putting out a good charge. The earth link looked okay and was tight, but wasn't giving a good earth on the test meter, so it was removed, cleaned and re-fitted to good effect.
Help! Battery or Alternator? - Ivor E Tower
You may have some other fault that is draining the battery too - check current drain with engine and all electrics switched off (this will require the multi-meter!).

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