Alternator light on.

[wyke]

1256 1975 Chevette - warning light on very dimly - does it mean it needs replacing ?
Tightened up belt but it is still on low - how do I test - or get a replacement ?
Thanks
G

[lambaj]

Means one of a couple of possible things:
Alternator is putting out to few volts, so not charging battery
Alternator is putting out to many volts, overcharging battery
Regulator is stuffed, so too many or to few volts.

What happens if you rev the engine ? does it go out, or get brighter or not change ?
Tony (HA21)

[wyke]

Rev egine and it still says dim.

[pbottomley]

*Bleep* earth link?

[turbo hpf]

you need a volt meter..then..
check light not on with out ignition (not earthing out then)
check light on with ign, power to alternator to energize regulator
all power off check with meter over 12.2 volts at battery
12.2=flat battery
12.6=half charged
12.8 full charge
all above approx and on good battery
start car you may need to rev engine to 3k to kick start alt working
recheck meter should now read 13.3 to 14.5-15 volts (depends on car really
old stuff 14.5 max as a rule) at idle, lower than this and cars not really charging enough
next leave neg meter wire on battery take pos meter lead and push to clean metal on engine, meter should read no more than .3 volts, more than this and you have bad earth(remove and clean wires and contact area
next goto back of alt find big red wire and pos meter lead to this ,it should read same as at battery or little bit lower this checks wire not broken or corroded to battery
if low check wiring to battery you are looking for high resistance.
using the meter even on the same wire across a terminal
ie battery terminal and same battery post will show this
good connection= close to zero on meter
bad connection =.5<volts electrickery will flow through your meter
rather than through corroed conector
hope that helps mike