i have an astra g coupe 2001 Z22se engine,
and i think i have a problem with the alternator, but not sure.
here it what it does.
when i start the engine i measure the voltage with a multimeter at 13.6-13.8V, after driving a while the alternator stops working i think, and i runn only on battery and the voltage starts to drop until 12v-12,4...sometimes even below 12V. if i happen to stop the engine i can't start it again..because my battery is dead.
sometimes it keep the battery around 12.8V....it's never the same.
sometimes the alternator is working great...once i had 14V when idling.
what can be the problem? the alternator , the regulator? or something else?
yesterday i went to a garrage and took off the alternator, cleaned the ground screw of corrosion, had a look at the regulator...but it's all plastic..can not open it
any ideea will be great!