Battery light comes on at high RPMs

[HighRev85]

So this has just been bugging me lately:

When merging onto the highway and leaving the car in third, the battery light will come on when the engine maintains high (greater than 4,000) RPMs for more than 5 seconds or so. The battery light remains lit for a good while (sometimes upwards of 3-4 minutes) when returned to a lower RPM. I have a gauge in the car that monitors battery voltage and, when this occurs, remains around 14 V. Is this an alternator issue, or is it something else that I'm not seeing?

Thanks in advance.

 

[HighRev85]

Oh yeah, 3.0L MTX, recent (2-3 years) alternator rebuild, battery ok (tested at AutoZone)

 

[SHO5OH]

This happened to me (and still does) on my 99 after I had the alternator replaced. I posted a question about it here and I believe it was Mr. Anonymous that stated it maybe due to the mechanic putting the wrong size alternator pulley on. Mine does go off right after the rpm's go down so I'm not sure if it's the same problem.

 

[Howdy_Doody]

Mine does this too, but it's more of a flicker. I've replaced regulator and brushes, and also put a new terminal plug end on from a junkyard car. I've concluded that my alternator stator is a little wobbly or rough. It's more an annoyance for me, and I've heard enough stories on rebuilt alternators that I'm not ready to try replacing the entire unit.

In your case, since it lasts for a few minutes, I would try installing new brushes and see if that helps. You can change them on the car if you're careful. Some small torx screws to remove (and not drop). They only cost about $5.

 

[HighRev85]

That sounds good...I figured it was something to do with the alternator. I'll check the status of the brushes. Thanks for all the advice.

 

[Slo-Sho]

Fried a diode or two.

 

[I'll sho u]

Check the small plug with one wire,It may have a bad conection.If it is loose it may cause the light to come on but still charge.Probably not a internal alt problem if still charging.

 

[duckrider]

i had this also, but i believe it was because of my bad motor mounts causing the motor to shift and move the small wire on top of the alt.... causing it to move back and forth, when it first started i had my alt checked and it was charging good, have you checked your motor mounts...? a good sign that they are bad is a polished spot on the intake manifold.... just an idea

 

[fast4door]

i had this also, but i believe it was because of my bad motor mounts causing the motor to shift and move the small wire on top of the alt.... causing it to move back and forth, when it first started i had my alt checked and it was charging good, have you checked your motor mounts...? a good sign that they are bad is a polished spot on the intake manifold.... just an idea

yep that was it for me. The battery light came one and my car died that day and i took it to a shop and it was my front motor mount and tanny mount. cost a lot to replace but havent had a problem afterwords

 

[HighRev85]

Motor mount...wow. Didn't think about that, but I guess that makes sense. I'll take a look today and see how it looks.

Thanks for the help!