Battery Light On, But Wait There Is More.

[elrodvoss]

So I have an intermittent issue with my battery light coming on. I replaced the battery and was working fine for a bit. I do have a spare alternator, but the issue may be deeper then that.

So I have a diagnostic reader that connects to my phone (ZUS), so I am able to get real time readings. Yesterday I am getting a reading of 12.0-12.1 from the battery reading and the battery light is on. The odd thing is I am not getting ANY other readings from the port. No load, no speed, no RPM, no O2 mix, nothing. I can get battery readings when the car is off.

The car runs fine, lights work, and voltage never drops below 11.8-12.0 during my normal 15-20 min drive to work/home.

Once and a great while, I get a rough start, like the battery is low, but it will turn over. This is why I started to use the diagnostic ready to monitor the voltage reading in real time. Last time the battery light did this, the indicator just turned off and my voltage jumped to 13.9-14.1.

As stated I do have the spare alternator, but could this be a computer issue, due to the fact that the diagnostic port is not getting any signal other then from voltage?

Thanks in advance.

[joatmon]

I don't know but I'd be inclined to swap in the spare alternator and see if behaves differently

[tpollauf]

What climate does this Vibe get driven in (update profile for us)? If high mileage and excessive corrosion, then you could begin to start having GROUND issues. Was there any major work done to the Vibe prior to this problem happening? The old saying "90% of all automotive electrical issues are due to faulty grounds" becomes more true as our cars age!

[elrodvoss]

Far south Chicago,. Kankakee County.

Biggest repair done was timing belt replacement, but this started well after that was done. (Several months).

Since we took off the alternator and everyrhing else on that side, one of the wires could be loose or short. Just odd how very intermittent.

[andrewclaus]

<12.0 volts while driving is way too low--the battery's not charging. I agree, check and clean grounds. Also check and clean connections at the alternator. Then replace the alternator. It could be an intermittent regulator circuit.

[elrodvoss]

Took to a friend, they checked alternator and it was bad. So something intermittent.

Put new one in and seems to be working fine. Voltage is 13.8-14.1 now night driving.

Thr diagnostic port started to work before he checked it out. Not sure the story on that one.

But all seem well. Thanks to all.