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

 

Start at the alt and check each connection. A battery going bad causes the alt to go fullfield and tends to overheat connectors. Check all connections/grounds and fuses.

 

thanks, i checked all of that . and it is still a problem. i replaced the alt and batt. at the same time. and the batt. goes bad not dead but bad. the " old alt " i replaced was good still, a $175. mistake. all the connections are clean and tight. baffleing

 

There is alot more to the charging circuit than an alt. That circuit goes through the PCM/CPU/interior fuse block/underhood fuse block. You posted that you replaced the original battery so i assumed it went south on you. I assume that was when the damage to the circuit was done. I do not have the car in front of me so i can only do so much with what info you post. You say the battery goes dead but do not say if it goes dead driving or just sitting parked overtime. If it goes dead parked but not driving then check for a draw. If it goes dead driving post the alt output at idle as well as the amperage output. Does the battery light still stay on? You have a problem in the circuit somewhere and if it is not a fuse or the alt then it is in the wiring/PCM/CPU etc. A wiring diagram of the circuit and then a thorough trace/testing of the circuit is needed. Only you or a tech can do that as we do not have the car in front of us.

 

the batt. dies whle driving it , daylight hours. the batt. lite stays on. I will dig deaper into what you montioned. 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