I have a 97 JDM ITR in my EX and just started having an issue with my charging system. I just got the alternator and battery replaced and they both tested as working by them selves. the back of the alternator reads 14V+- yet they battery reads about 12.4-12.6V while running. The car will run for about a week (200 miles) then the battery drops down to a point where I cannot start it. I don't really know where to start in the diagnostic process. Can any of you give me some ideas of where to start?

Thanks much!

 

Voltage at batt. should be about 12.5V, [engine not running] about 13.5V, [engine idling] and up to 14.5V, [engine RPM up].

12.4-12.5 with engine running indicates a problem with the alt. or voltage regulator, or possibly wiring, test the voltage at the "charge" wire on the alt. then teat it at the "charge" wire connection at the engine bay fuse box.

Or take the car to just about any alt./batt. shop, [like Interstate Batteries] and have them do a proper load/gravity test, it will only take a few min. and it will be free. 94