i have a 2002 protege 5 one night the battery died. I replaced it . and the batt. light came on immediately.
I then replaced the alternater, (all going off local parts houses advice and testing intraments) then the car did the same thing . I took the "old" alternater in for a bench test and it was good. the batteries are dying, loosing power? i have no clue

 

Check the battery terminals at both ends. Check all the ground points. Is there something drawing it down??? Lights, etc.

 

i will do that thank you . this does it with nothing powered up.

 

Could the belt be slipping? Did you recently install a new electronic device?
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belts are tight. all stock electronics.

 

I would take it someplace that can test the output of the alternator when it is in the car under load. You can use a multimeter to measure the voltage at the battery with the car running. The next thing you will want to do is check the amperage the car is drawing. You'll need to find someone who has an electrical system diagnostic tool. If you can get this done, check the starter to see if it is drawing unnecesary amperage.

 

right on, thanks i will do this monday and will post the out come . thanks

 

i took it to the mazda dealer it is the ecm. this is covered by the manufacture warranty . 8 year 80000. i bought it used from a nissan dealer as is with 54000 miles on it. i lucked out.

 

Boy did you ever! I'm sure that a new ECM would have cost you a pretty penny.
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At least $100 for a used one, plus anything else they may have crapped out further down the line. That would make sense it would be drawing down the battery. Gotta love the Mazda warranty...