the common cause why the light is on is that your alternator is not working well,try to have your alternator checked .may be the carbon brush is already worn out.
No. If the alternator is working fine, the battery power is not used.
Charging system is not working properly. Have the alternator tested at any auto parts store for free.
needs a coil or distributor it could also be that the alternator isn't working and the car may be draining the battery every time you drive it
the battery will not charge.eventually when battery is flat the car will not run either as both battery and alternator ,togeher complete the electrical circuit
It doesn't actually drain the battery, but without a working alternator to recharge the battery it will only discharge as the car is operated.
It depends on what kind of car you are working on, but it sounds like it can be an external voltage regulator, or even a fuse Some vehicles do not charge with out a rpm signal. The cause of the tach not working may also fix the alternator.
alternator is not working so your battery isn't getting a charge
Depends on how low the battery is but give it 10-15 minutes and it will be fully charged, assuming the alternator is working properly.
Most likely your alternator is not working properly.
The voltage regulator is not working properly.
I am having the same problem with a 99 Protege. I have changed the alternator and aligned/cleaned the pulleys and the problem persists.I replaced the alternator, on my 1997 Mazda Protege, seven times before someone figured out why the serpentine belt kept breaking. It was the belt tensioner! It had to be removed and rebuilt. Now it is working like a charm!! And I havn't had to replace the alternator in over 3 months!!!!