My 90 miata battery keeps draining
 

ok so i thought i had a bad cell in my old battery. the car would drive for about 20min sit go to start again and would be dead. once in a while the battery charge light would flash. so went to Autozone today bought new battery. get home from work try to start the car again after JUST driving it battery is dead wont start the car, but the radio/lights all work. WHAT SHOULD I REPLACE NEXT? im thinking the Alt. or should i be looking at something more simple?

Have a multimeter? Check battery voltage when the car is running. Should be about 14.1 volts if your alternator is working.

ok thx

how long is it sitting before it dies. If you let it sit for a long time you may have to large of a dark current drain, but sounds like may be your alt.

it can sit about 1 min or overnight, both have happened

Check your ground cable for breaks.

thx guys for all the help. Alt. is totally dead. what is the easyest way to replace it? put the car on a lift? or can it all be done from above?

Easily be done from above. It would be alot easier if you remove your intake manifold though.

are there 2 or 3 bolts?

If i remember correctly you will need to loosen the adjustment bracket remove the bolt from the rear of the bracket into the alternator and the bolt on the bottom of the alternator. So it is a total of 2 bolts to remove and one to loosen. I just had to replace alternator on my integra yesterday luckily I had a spare already.

thank you. i havent picked up a haynes manual yet, but thats my next buy :)