Basically, in my 2002 Civic EX 2Dr coupe my battery light is on. My brother in law is a mechanic and he and I spent all day trying to investigate all the obvious things. I just replaced the battery and today we replaced the alternator hoping that would solve the problem. Obviously that didn't do the trick. We used and OEM alternator to replace it. We didn't have access to a code scan tool but we checked all the fuses and like I said all the obvious things with no success. Anyone have any ideas where to look in the meantime?

 

I have always read and heard that if the battery light is on, it means one of two things,
A. the Alternator is not charging
B. the Battery may be defective.

I see you have already investigated the obvious so your on the right track.

Have you used a tester to verify that the alternator wiring is not defective in some way, running from the alternator to your battery, or maybe a loose or bad ground?

Have you contacted a dealer over the phone with similar questions?

These are the only 2 questions that come to mind, I haven't had alot of electrical issues over the past few years, but I know loose wires often cause a painstaking problem. You might try a tester and check the wiring to and from the alternator, and perhaps monitor the battery over the course of a day or so, see if the sitting voltage drops alot for no reason, you might have something grounding or a faulty switch somewhere causing the light to be on.

 

i would start checking the wires. maybe something is grounding out that shouldnt be or something

 

Start the engine and then look at the battery voltage. The alternator onthe 2001-2004 Civic will take the battery voltage up to 14.5 Volts when it is working properly. A battery voltage of 12.7 or less will mean the alternator output is not up to snuff. On the 2001-2004 Civic there is an 80Amp fuse between the alternator output and the battery + terminal, assume this has been checked. Also, on the 2001-2004, there is a 10Amp fuse under the dash for an alternatorIGN input.

 

There are 5 wires to the alternator plus chassis ground, they are:
1. Terminal B, BLK to Fuse 19, 80Amps and then to the Battery +
2. Terminal C, WHT/GRN to ALTERNATOR CNTRL SIGNALin the ECM/PCM
3. Terminal FR, WHT/RED to ALTERNATOR FR SIGNALin the ECM/PCM
4. Terminal L, WHT/BLU to ALTERNATOR L SIGNAL in the ECM/PCM.
5. Terminal IG, BLK/YEL to Fuse 4, 10Amps HOT (+12V)in IGN ON or IGN START.

 

I have checked the battery voltage and it maintains a steady 14.5-14.8volts even when all other systems are running. I looked at the harness and checked all the fuses as well. I can't see anything that is obvious put I haven't done any point to point wire checks to see if there is a break in the wiring. It just seems very odd to me that the system is still charging like normal but that light continues to stay on. Has anyone ever had something in the dash itself go bad causing the light to malfunction?

 

I tried all of the obvious things that everyone has stated and thanks for the help by the way. I just can't figure out why when the system appears to be charging at normal (14.5-14.8) when all the systems are running and the battery light remains on. I have a chilton's manual and have tried to trace through the wiring to see if there is anything there but everything seems functional. Does anyone know of any glitches that the ECM may cause?

 

Have you tried forcing a "Maintenance RequiredIndicator" Reset procedure: To do this,TURN the IGNITION OFF, push and hold the Odometer TripReset Buttonand HOLD IN.Turn on the IGNITION, wait 10 seconds and then release the Reset Button. The procedure is in the manual if I did not do a good job of describing. Just a hunch, because the "Charging System Indicator" is controlled by the same Guage CPU as the "Maintenance Required Indicator" and the signal from the ECMto this Guage CPU comes in the form of a communications link (SEFMJ) which carries a lot of other information that we know is working.

 

I tried that and it let the battery light turn off but as soon as I started the engine the light came back on. I am beginning to wonder if I don't have a module or ELD going bad. I am guessing it's not the ELD because the alternator is charging but who knows. Is there any way to diagnose the ELD elctrically to see if it's intermittent or something.

 

If all else fails, and the car works correctly every time you start and drive it, a small strip of electrical tape over that light works wonders :-)

I used to drive a car that had like 5 lights on all the time, dealers said it was normal ?? Ok mr. dealer guy.