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My car is a 2007 Honda Civic LX Sedan. One day the battery light came on and then off on the way to school, on the way home my alternator gave out. My mechanic replaced my alternator but suggested that their might be another issue causing it to go bad. The next day the battery light came on again and the alternator was not charging properly when tested. Something kept frying the alternators, so he traced it back to the PCM and we replaced that. It went fine for a week or two and then battery light came on again. We figured that the refurbished alternator that we put in was just a lemon, so he warrantied it out and replaced it with another one only to find that it charged perfectly fine outside of the car. I tried to drive it to his house, about 25 miles away, and the alternator died again. He used the diagnostic chart to trace it back to the ELD and determined that the ELD must be the issue causing all of this. We replaced the ELD and the car ran fine, but six days later the battery light came on again. I got it tested and yet again the alternator was not charging enough (12.21V W/o load) and the battery tested fine. So then I went ahead and replaced the entire under the hood fusebox yesterday, that didn't solve the problem. This is the first time I've ever turned to asking the internet for help on anything.... the matter has been rather frustrating as I have not had a reliable source of transportation for months now and money is tight. I searched on the forum for similar threads and couldn't find any. Several google searches and multiple youtube videos have turned up nothing. Can anyone provide some insight on whats happening?

 
Rep Power: 518

How about a simple diag process:

Drive it until the charge warning light comes on.

Leave it running, open hood:
Unplug the 4-wire connector from the alternator.
Does that make the charge warning light turn off?

Reconnect the plug. Is the warning light on again?
This can be normal and OK at times. Read up on how Hondas ELD controlled charging system is supposed to work.

 
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Thank you for your reply ezone. The mechanic who replaced my fusebox yesterday did the same test. The battery light would go off but then come back on not even 30 seconds after the alternator being re-plugged or the engine being turned back on after being off. I did read a report earlier that described Honda's dual-mode charging system. I read that in "low output mode," which occurs during start-up and light electrical loads, that the ECM should set charging at 12.4-12.9V. The report also suggests that in issues of low-charging: "if the C circuit is shorted to ground, the charging system will always charge at the low output mode." What has happened every time with this car is that every time we replace a part that is supposed to be causing the problem the alternator will charge fine for a little while but then begin to slowly charge less and less until the car eventually runs off of the battery and dies. The car is now at my mechanics house and he says he is going to rewire the charging system. The report I was referring to is this one: http://opensiuc.lib.siu.edu/cgi/view...text=auto_pres

 
Rep Power: 518

Wait, hold up. You skimmed right past specific answers.

I wanted you to do these yourself and tell me the result at each question:

Reason: I want to figure out if the alternator has control of the warning light, or if some other control unit in the car is turning the light on.

This should have been a stupid simple diag here. If the warning light turns off when you unplug the alternator and it comes back on when you reconnect it, the alternator is the problem.



Maybe all it really needed in the first place was a quality alternator from Honda instead of discount parts store cheapo units.




It can drop into the 11 volt range too.

 
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I wish I could do the diagnosis but unfortunately the car is at my mechanics house and well, I have no car to get there. I also wish I could have afforded a Honda alternator when this all started happening, but the college student life is not too financially rewarding. I figure that the PCM would have just fried it anyways though as it did with the one before that and the next one that was put in.

I thought the mechanic did the same simple diag test with the alternator yesterday, but I may be mistaken as I was just watching and know close to nothing about how a cars charging mechanism works.

I guess I'll just have to wait and see what my mechanic comes up with. I appreciate all of the help and insight you went out of your way to give. I was hoping this would be a problem someone else has had before and knew the answer too but I suppose it could be one of many different electrical issues at this point.

That Alva board is sick by the way.

 
Rep Power: 518

Yes I deal with similar problems all too often. That's why my first guess is "Crap reman cheapo alternator" probably from The Zone.

Where did the PCM come from anyway? Is it a reman too?



FYI I went with the cheapo but lifetime guaranteed starter for my GFs sons Honda CRV (he could not wait a day for a Honda unit).....Aaaand on Dec. 23rd I just replaced it again for the 3rd time in less than a year.....
I'm still kicking myself because I should know better by now.

Thanx