I was coming home from baltimore today and my battery light came on when i was leaving. I assumed the alternator was going bad so i shut off radio a/c etc hoping to make it home(130 miles trip), about 80 miles into the trip the light went off. I drove the last 20 miles or so with lights,a/c, radio, defrosters etc on to see if the light would come back on and it didnt. I had the battery and alternator tested at autozone, the battery tested good, and the charging system was only reading like 11.5 volts with no output from the alternator. im not really convinced their machine was working properly. i spoke to my mechanic and he said there is no way i would have my it home if my alternator was bad and suggested the battery being the problem. anyone else have similar problems or any other input. thanks in advance.

 

ur alty could sparatcially be charging........i drove a full day on my optima with no alty

 

yea I had that problem my light came on, on my way home from salem, nj about 30 miles half way there the light came on then went off then came on later that night and after that it stayed on for that next morning and by that next night my battery was dead...maybe its a warning feature? idk but I think it comes on when ever the volts get below 12.5

 

its probably the alty... my girlfriends car used to do that.. she would drive for 15 minutes and the car would go dead.. it was pretty funny

 

Generally, the charging system is pretty simple. I would be more concerned with an intermittent wiring issue. generally, the alternator will either charge or not (there is always exceptions). I had an older Nissan come in the shop a while ago and it had a connector which was corroding causing an intermittent condition. Before you throw a nice expensive alternator at it, check the wiring very very carefully. Make sure you have power and grounds in the correct places. It is always possible to have a bad alternator or battery, but check the basics. If you need help figuring out what wire does what, email me at mikem29ss@hotmail.com and I will get the schematic at work and help you out. good luck,

Mike

 

I guess if the light come back on and I still make it home i'm going to grab a new battery and then check over the wiring and make sure nothings loose or corroded. Maybe it was just some freak thing to happen?????

 

When the light comes back on, disconnect the battery while it is running. If the battery is bad the system will start working properly. If there is another problem and the alt is not putting out, it will stop running. Simple test but effective.

 

not the best idea to disconnect a battery while the car is running, voltage spikes can damage electronics. best use a tester hooked up properly. sears will test the system for you.

 

It gets the job done. Any voltage spike will be minimal and won't damage anything. No more than having an intermittanly shorting battery. I don't think that is the problem anyways. but it was a suggestion to aide in the diagnosis of an intermittent problem.

 

The battery light came on again yesterday, I turned everything on that would draw from the battery and the light went out a few minutes later. I put a new optima in it lastnight so we'll see if that does anything.

 

Does engine speed play any factor in when this light comes on? I previously had an alternator go bad, but it was only a problem while driving. I was cruising on the freeway when my CD player started shutting off, my lights got dimmer, and other electronic features didn't work as they were supposed to. If I remember right, the battery light was on. I pulled over and everything sprung back to life. Then I drove again and the problem came back. I pulled over again, and everything worked fine. This went on and on until I made it back to the last town.

It turns out a wire had been fried (literally torn apart) inside the alternator and would not carry a spark when the alternator was turning fast (i.e. driving), but the current would arc the gap and charge the system when the alternator was turning slowly (i.e. idling).

 

[QUOTE=isawyou]Does engine speed play any factor in when this light comes on? QUOTE]


No it doesnt seem to. First time it came on was right when I started the carand then remained on as I traveled the highwayfor about 70 miles, second time it came on was doing about 55 and cruisin. Drove about 200 miles yesterday and no light with the new battery, will drive anohter 100+ today and see what happens.

 

Dont forget to also check your fuses, the ones in the engine bay. You got like 3 you should check.