Random battery indicator light

[Dad]

This thing will come on while driving down the road, but when I come to a stop it goes off. Might come back on, might not. The battery is about 3 years old and so is the alternator. I can't remember the exact voltages, but with the car off it showed around 12.3 ish volts and with it idling it was around 14.9 or so. That seems high, but I dunno. I did not check what it was at around 2k RPM.

 

[86GT351]

I have seen Alternators show good when they are actually bad.

 

[Juice]

Need a voltage reading when the light is on to see if is actually not charging. But I think you have an alternator going out.

 

[Dad]

I just drove it a few minutes ago and noticed it only comes on between 1000 and 2000 RPM. If I am driving say below 70. If it comes on and I shift to neutral and give a quick rev, light goes off. Sounds like alternator to me as well. I doubt I can find my receipt and I don't remember where I bought the thing. I tend to get the lifetime warranty on things like this, but they wouldn't honor it until it fails completely. Which would be at night in the rain in the middle of nowhere.

 

[TexasBlownV8]

Alternator. Had one do something similar recently on a '07 4.0. Also make sure the battery cables are clean and tight.

 

[Dad]

New alt should arrive this afternoon. Interesting info to add though. Yesterday on the way home from work, the radio went off. Weird. So I shut off the headlights and the radio came back on. Battery light was NOT on when it happened. Anyway, made it home and shut it off. After about 10 minutes I went back out and it started right up. I put the charger on it anyway and it appears to be no change from yesterday. Light randomly came on today, went off at a stop, etc. Battery connections are tight. I did not pop them off to see how clean they are, but I will do that when I change the alt.

 

[86GT351]

New alt should arrive this afternoon. Interesting info to add though. Yesterday on the way home from work, the radio went off. Weird. So I shut off the headlights and the radio came back on. Battery light was NOT on when it happened. Anyway, made it home and shut it off. After about 10 minutes I went back out and it started right up. I put the charger on it anyway and it appears to be no change from yesterday. Light randomly came on today, went off at a stop, etc. Battery connections are tight. I did not pop them off to see how clean they are, but I will do that when I change the alt.

Remember everything accessory related goes through the Smart Junction Box in the passenger foot well. Along with the Alternator. If the direct source (Alternator) is defective, other components can and will act up.

 

[Dad]

Alternator replaced, all is well.