Battery charging system light on

[croberts26]

2006 Vibe wth 155,000 miles.

Battery light came on last week after the battery kept going dead. I bought a new battery and the car is working fine but the light is still on. I took it to the shop and both the battery and alternator outputs are within their normal ranges. I cleaned both battery terminals and made sure the ground wire for the battery was clean. Light is still on.

Any thoughts?

Thanks

[bluneon]

I took it to the shop and both the battery and alternator outputs are within their normal ranges.

can you elaborate? what did the shoppe describe as 'normal range' for an alternator?

normal voltage for a battery is 12-13 volts. normal range output for an alternator under no load is around 14 volts. 14 volts because you need to power the electronics while driving, to keep the car running and to help recharge the battery while running.

the charging system warning light only comes on when there is a voltage issue, either the alternator is overcharging or undercharging.

[croberts26]

I went ahead and changed the alternator. Light is still on. Fog lamps are not working. Daytime running lights are not working either. Can it be a blown fuse?

[bluneon]

do you have a multimeter?

start the car, allow it to run until open loop warmup is completed (normal idle, not warmup idle speed). turn off all loads inside the car, measure the voltage between both battery posts. what is it reading? it must be reading around 14 volts.

new battery, new alternator. i would check fuses. possible there might have been an amperage spike that blew out some fuses.

[croberts26]

It was a blown charging system fuse. Thanks. Cr

[lannvouivre]

It was a blown charging system fuse. Thanks. Cr

Did you already get rid of the old alternator?

[Caretaker]

Am I screwed? Yesterday (90+ degrees) I drove 15 miles to Costco to get gas and do chores. Just as I pull up to the pump, my battery light comes on. I turn the car off and then cannot restart it; just clicking noise from the starter. I push the car out of the line and get a jump start. The car hesitates to start, but does. Figuring my 4 years old Costco battery is failing, I drive over to the tire center to get a new one only to feel that the electric steering is not operating properly for the 300 yard drive. With manual steering, I park the car in the tire center's lot, being careful to back in in case the car dies again. After calling my mechanic on the phone, he says it cannot be the battery and probably is the alternator. After 15 or so minutes, of buying a new battery and then returning it as my mechanic instructed, I go out to the car to find it won't start again. I get a second jump, with the car starting but not providing any electric steering. I drove 3 blocks over to an NTB to have them do a test of the system. 2 hours later I get a call from NTB that the car started fine and the battery and alternator tested fine; no problems. I'm flabbergasted. I decided to take a big risk and drive the car 20 miles to my mechanic. I made it fine with the electric steering working just fine. I did not use the A/C the entire trip for fear of putting too much load on the car. 2 hours after I drop the car off with my mechanic, he tells me that NTB was correct; everything was testing fine. I have asked him to put in a new alternator since I didn't make up being stranded twice in an hour.
After doing a lot of research on-line last night, I see that there are a lot of reports of overheating alternators. That would explain why the car started up just fine at NTB after a 1-2 hour rest. The question is, what is actually wrong? Is the 6 year old alternator failing or is there something making the alternator fail by drawing too much power? The last thing I need is an electrical problem when I'm 2 months away from driving across the country for a move.
To recap: 4 year old (March 2011) Costco battery; I keep the cells full with distilled water. 18 month old Denso starter. Can a problem with the battery play a roll with the alternator or is it true that once the car is started, the battery plays no part in operations since the alternator takes over? Since the alternator is supposed to keep the battery charged, in my mind, there is still some "connection" between the battery and alternator. Thanks in advance for your thoughts.

[GOF]

I would be willing to bet that the alternator was the issue. I wouldn't bet the a case of beer, but would certainly risk a six pack. There is a small chance that the battery could have shorted internally and dragged the whole system down. But that is unlikely. I would expect the battery to burn itself out if it was the culprit. Likewise for a short elsewhere. Probably something in the alternator that expands and breaks the contact internally. Alternately it could be something in the wiring of the system. If it were my car I would look at the wiring for damage or corrosion and then just drive it.

[Caretaker]

Thanks for the reply. I am having the alternator replaced as we type. My mechanic said that if I have the same failure again in the coming week or so, he'll put back in my old alternator and give me my money back. I also will go to Costco and get a new battery since the NTB test showed that the CCAs were running in the 300's when it should be 500's. Also, I do recall smelling a burnt rubber smell when I popped the hood yesterday after it failed the first time. I have read reports of that same smell with a failing alternator/regulator, which I'm told are now all together in the alternator (no longer separate parts). I do hope you are right that it is simply the alternator and we can move on. Again, I greatly appreciate you taking the time to respond.

[GOF]

Do keep in mind that charging problems can have a detrimental effect on a battery. It is possible that the battery can be going bad in addition to a failure of the alternator. But the CCA (cold cranking amps) only comes into direct play when starting. The lower CCA wouldn't really be a problem while the engine is running. While running the battery acts more or less like a capacitor evening out the alternators output. Not saying your battery is good. But I don't think it explains the issues while running.

[bluneon]

basic automotive electrical system components must work together. if one component fails then the rest of the system will be under extreme pressure to keep the engine running.

if your alternator took a crap then the battery light will come on. the alternator may be completely dead or simply not producing sufficient voltage. continuing to operate the vehicle while the alternator is undercharging will lead to a discharged battery. if there isn't enough voltage being returned to the battery while driving then after some time the car will die and the battery will be dead/discharged. in short: if the alternator dies while driving the only source of electrical power left to keep the car running is the battery.

with a very dead battery the engine will start when attempting to jump start, but once the jumper cables are removed the engine will stall out. that's because the dead battery is sucking up all of the voltage the alternator is producing (even if the alternator is good). leaving the jumper cables on for a little will help recharge the battery, or raise idle a little to keep the engine running.

[GOF]

Best to hook up the cables and let the battery charge for a bit. Then start the car. Not a fan of leaving the cables hooked up after the car has started.