alternator or something else?

[magnetnerd]

A couple days ago my low battery light came on. I went to Advance and had them check my battery and alternator, both of which checked good. (the battery was low though, and it's only a couple months old)

I noticed that the light shuts off at higher rpm's (higher than I usually drive), but it comes back on when the rpm's drop again.

Ideas?

 

[RangerSVT]

Was the altenator tested on or off the truck?? How are your battery terminals (clean/corroded)?? altenator plugs clean, wires in good shape??
SVT

 

[magnetnerd]

Alternator was tested on the truck.

Battery terminals are good.

Alternator plugs and wires look to be okay...?

 

[RangerSVT]

What's your truck idle at when the light comes on?? Do you have aftermarket pulley's?? ( I take it the truck in question is in your info....)
SVT

 

[magnetnerd]

What's your truck idle at when the light comes on?? Do you have aftermarket pulley's?? ( I take it the truck in question is in your info....)
SVT

Idle as in RPM or voltage? RPM I have no way of knowing because I don't have a tach, and voltage...well, I don't have a multimeter so I don't know that either, haha.

Stock pulley's, and yes, the truck is the one in my info.

 

[magnetnerd]

Update: I brought my truck to my dad's tonight and we put the multimeter on it. 11.5 when the truck is off, and 11.1 at idle. Soooo...bad alternator, yes?

Is the voltage regulator normally included with an alternator or no?

 

[RangerSVT]

Yes, voltage regulator is internal, check voltage at 2k rpm, but it should be no less than 13.0 at idle (13.5-15.0 is optimal range), also, check voltage with engine off, as it should be no less than 12.5 with a fully charged battery...
SVT