Astra Battery/Alternator Warning Light - What Could Cause It To Come On?

Hi All,

Recently started having problems with the battery/alternator warning light
on my '93 Astra 1.4i. A few weeks ago (during that horrendous weather) the
fanbelt started squealing, resulting in the warning light illuminating to
varying degrees.

I replaced the belt on Wednesday and as far as I can tell it is a more or
less the correct tension (~0.5 inch play), but the light still insists on
illuminating. Usually it is relatively dim (i.e. only really visible with
the dash lights turned down), but I've also found that when indicating
(bearing in mind I'm also running dipped headlights, fan on 1, rear
demister, wipers, headunit and sub/amp) the rev counter rises and falls
slightly and the warning light & headlights brighten & dim in time to the
flashing. I realise I'm putting a fair old strain on my cars electrical
system, but before it's had no problems coping.

The alternator was replaced just over a year ago, the battery (Varta, sealed
maintenance free) is approx 2.5 years old. However the battery has been
pretty much completely discharged 2 or 3 times (due to the failure of the
previous alternator).

I've got a nasty feeling that it's the battery causing this, but I always
thought that it simply 'regulated' the fluctuating voltage output from the
alternator, as opposed to powering the vehicle whilst running. What sort of
checks can I do on the electrical system in order to track down the location
of the fault?

Many thanks in advance!

Dan

 

Even though the battery is sealed, have you checked the electrolyte levels?

I had one a few years ago that needed topping up.

Dave

 

By far the easiest would be to fit another battery, even just a mate's one.
see if it goes away.
i doubt that a shafted battery would cause the ignition light to dimly glow,
so my thoughts lie with maybe the regulator pack/diodes in the alternator
being a bit sick somewhere.
but i also agree with your loading theory, it is alot to ask, so might just
be normal.

a basic check would be to measure the battery after standing for say a night
before starting.
should be well better than 12VDC, as high as 13VDC if it is in good nick.
start the car & the volts should climb with a maximum being about 14.5VDC at
high revs.
there is a point, (1200-1500rpm) where the alternator & it's box of tricks
should not let the volts go any higher across the battery.
if the volts continues to rise (over 14.5VDC) when going past about 2000rpm
then i'd go for a damaged battery.
if the volts across the battery never reaches into the 14VDC region,even
after a long run(when it should be fully charged)
then i'd plumb for a dicky alternator pack or maybe a suphated or buckled
plates fault with the battery.

best bet though, as i said, stick a mates battery on first.
that should give you a good pointer.
bearing in mind the battery age, i'd point my finger there!

mike

 

Check the earth wire at the gearbox for damage/corrosion.

 

Your fault description is just that of a failure of alternator rectifier
pack (built into alternator). If you measure battery voltage during idle and
its less than 13v that would just about seal it for me - another alternator
required.

Best of luck.