Ok, well I've done a search in this forum for battery light and it didn't help me so now I am going to put this out.

My g/f's 2001 civic ex is acting up. Her battery light came on the other day when she got off of work and threw her car out of wack. Her idling was screwed up and it felt like her car was going to die. Well she pulled it over and had AAA take it to the shop because she didn't want to trust driving it 20 miles home. I told her it was either her battery or alternator so she wanted to take it to the shop to know for sure. Well it sat at the shop overnight and when the mechs went to work on it the next day the problem was gone and her car ran perfect. They load tested the battery and the alternator and they tested good. Well she still had the original battery in the car so I changed it out with a duralast and checked her alternator belt to make sure it was tight which it was.

So yesterday the car ran fine, no problems. Today on her way home from work again the light came back on (2 days after the battery change). It was on when she came to a stop, but once she hit 3500 rpms it went away, until she went below 3500(this is in stop and go traffic downtown). Once she got to where she get it to 3500 rpms and keep it constant the light went away and has not come back.

Now the only thing I can think of it would be the alternator but I would think if the alternator goes bad it is going to go completely bad, and not charge at all, as opposed to charging some of the time. Does anyone know of an alternator only charging some of the time and being "kind of bad"? If anyone has had any experience with this or has any suggestions I would appreciate it. Thankyou.

 

Alternator performance can decrease over time, or even be erratic. Alternator output tests that use the battery tester are only so accurate. Take a DVOM and place the leads across the battery terminals(positive to positive, negative to negative). If it is below, say about 13.6 volts replace it.

Alternators can start going bad but not throw the batter light on. For instance, if the SRS comes on and goes out spuratically without a DTC, the alternator output may be low enough that the capacitors in the SRS unit are not being charged, yet the battery light is not coming on. Alternators can also go in a heartbeat. The alternator in my accord tripped the battery light and then died completely in the space of about 2 hours.


Sounds like the alternator to me.

 

Sounds like alternator brushes are wearing out. The only way to diagnose is to test parts of the car when the symptom is present. That's the hard part about intermittent problems. Does the light come on at 3500rpm at idle, or just while driving?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by phootbag &raquo;</TD></TR><TR><TD CLASS="quote">Sounds like alternator brushes are wearing out. The only way to diagnose is to test parts of the car when the symptom is present. That's the hard part about intermittent problems. Does the light come on at 3500rpm at idle, or just while driving?</TD></TR></TABLE>

At idle as well as driving. If she is at a stop light while the battery light is on and revs it passed 3500 the light will go off, but then come back on after it goes back below 3500.

 

anyone else with any more suggestions?

 

I blew through a battery and a month later an alternator. It seemed like it was time for a new alternator so I replaced it without question (it was making a terrible noise). Now 3 months later I have blown another alternator - took it to a different mechanic who said there's a service bulletin about this. I can't find it anywhere, but he says there's a bad switch in the circuit that's $50 to replace. I had him change it, but am pretty irritated at going through 2 alternators in 4 months. Does this sound plausible to anyone else?