2007 Mazda3 2.3L Electrical Issues

My battery went dead because I forgot to close the trunk so the dome light stayed on. I boosted my car with no issues and went for a drive. During my drive (about an hour in) the power steering light came on and I lost power steering. Then a few minutes later, the ABS light came on, then the handbrake light, then the airbag light, then the radio cut out. Finally, all the lights (interior and exterior) began flashing very quickly. I pulled over and shut he car off. It would not restart on its own or with a boost. The car lights up as usual when in "run", but it turns over very slowly and does not start. Does anyone have any idea what it could be? The battery seems to be fine, but wouldn't having a boost eliminate any issues with the battery? Thanks.
 
Most likely you need a new battery. Some things to do...
1) Get the battery tested
2) Get your alternator tested
 
I replaced the alternator and the car worked perfectly for a couple of days. Now it won't start again. The engine doesn't even turn over when I turn the key. The battery may be the problem.
 
If the battery is less than 4 years old, you should attempt to fully charge it. If it cannot reach full charge, it is likely no good. Alternators rarely fail, so unless the battery fully charges, yet that charge won't last after a few days of typical driving, then the alternator is okay.
 
Back