Hey guys lookin for some help I have a 99 civic si and I am having some electrical issues. First issue is the battery not charging. Just today I replaced my alternator after realizing my battery was not charging after installing new alternator and finally getting car to start my rpm’s jumped up to around 2000 at Idel and after driving car for about 30 minutes when I go to start car battery is dead. With the car running my battery was reading about 11.25 volts I have a newer battery just replaced it last year but it did sit for a large majority of that time. All fuses have been checked and nothin looks out of place. I also believe I have a ground problem somewhere when I first got the car and scanned it I saw I had a code for a coolant temp sensor voltage high after replacing I still got the same code sometimes when working on the car before driving it the battery would die when I would hook up a test light inline with the battery and the battery wire it would turn on Indicating a draw I’m not so much worried about the sensor but I can’t figure out why the car won’t charge if anyone can help it would be much appreciated.

 

what's the voltage reading on the battery terminals with the engine off? A good battery should read at least 12.4VDC and up. If not, you need to replace the battery. Should have checked this before spending money on a new alternator.