3 days ago I was driving home, the engine was fully warmed so I turned on the defroster and it seemed like there was a drop in electric power. I noticed the battery light on my dash was on, went on and off a few times then just stayed on. Tested the battery when I 1st saw the light and it was around 12.6. It must of been around this time I wasn't getting any charge back in the battery. Drove around 7 miles to work. Tested and found slightly lower voltage. Got a jump start at work because I new the battery was weak and about 2-3 miles down the road it died on me. Cleaned the battery connectors and terminals and installed a new battery. Battery dash light still on. pushed in and wiggled plug to alternator, checked connections and wiring, nothing obvious. alternator spins with a correctly tightened belt. Checked fuse 15, its good. I've pulled the alternator and it passed the diode test but I haven't looked further. Are all 4 of the wires on the alternator plug supposed to have continuity with the negative wire that connects to the battery? the only one that doesn't is the wht/grn one. I checked the continuity of it from the alt plug to the computer and thats good but I don't know where to go beyond there. The bottom left off the computer case is rusted and corroded but internal components look fine. Anybody know what I should do? Thanks

 

Don'y really know about the 97 Civics
But, on my CRV, there is one big cable to alternator which comes from the 100 amp fuse which comes from the battery
The four others ... WHT/GRN and WHT/RED and WHT/BLU and BLK/YEL
One comes from the PCM which tells the alternator whether it is low or high charging mode (WHT/GRN)
Another comes from the PCM's field reference signal .. should have 5 volt to voltage regulator (WHT/RED)
Another goes to PCM's charge indicator lamp ... battery dash light (WHT/BLU)
The last one comes from the ignition and should be hot when ignition is on (BLK/Yel)
The PCM also gets another signal from the ELD electrical load detector.

The ELD tells the PCM whether there is a high demand load or low demand load
This then lets the PCM tell the alternator whether to be in high charging mode (hi load) or low charging mode (lo load)
The PCM also sends out a 5 volt field reference
The alternator then tells the PCM if it is charging or not
The ignition wire gives the alternator juice to power up its coils so it can produce power

Well, that is how I understand its operation.
If I am wrong or not getting it right then please let me know.
Thank you.

 

Reinstalled the ecu and did a full field test on the alternator, it failed. Opened it up and so far it looks like the capacitor in it is whats faulty. I'm gonna give it some charge and test it. Hopefully my new alternator arrives soon.