Vauxhall Astra G Petrol (1998 - 2004) - Battery and lights dimming at idle

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Tue 23 Oct 2007 13:30
Battery and lights dimming at idle - Kingpin
Hi there, I wondered if you could throw any light on an issue - this morning I noticed when idling in traffic (normal 900rpm) the dashboard display for date, time etc went brighter when I raised the engine revs, the headlamps were on at the time on dipped beam.
I thought it may be either the alternator not keeping enough charge at low rpm or else the battery is not 100% even though the green eye indicator looks fine.
It is a 2002 Astra 1.6 and I suspect on its original battery five years old. At the weekend I changed the timing belt, water pump and thermostat and refitted original alternator belt, it has one of those automatic tensioner wheels so I assume it's at the right tension.
I am considering fitting a new alternator drive belt, then cleaning up battery terminals before looking at the battery.
If you have a voltmeter can you test battery and alternator function by putting it across the terminals and it should be 12 volts or more as the engine increases?

Thanks
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Tue 23 Oct 2007 13:34
Battery and lights dimming at idle - RichardW
Sounds normal to me - alternator doesn't really get into its stride till over 1000 rpm. Battery should be > 12V engine off, and it should be around 14.5V with the engine running at approx 1500 rpm - may well be less at idle with lots of load on (you probably had HRW, blower, and lights on this morning?)
--
RichardW

Is it illogical? It must be Citroen....
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Tue 23 Oct 2007 13:39
Battery and lights dimming at idle - Glaikit Wee Scunner {P}
Sounds normal to me. But worthwhile doing the checks anyway.
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Tue 23 Oct 2007 14:48
Battery and lights dimming at idle - Kingpin
Cheers, thanks for replies. Yes it was probably under load with headlights and heater on. Will do basic checks and keep an eye on it's cranking speed. At this time of year you start to notice how cold affects batteries that are getting past it.
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