every so often the battery light will come on and gauge will go down low, but still in normal range...then it will pop back up normal and battery light will go off. it comes and goes, doesn't happen all the time. what could be the cause?

truck has a new battery. its a 97 ford f250 heavy duty, 5.8L 5 speed 4x4..257 thousand miles. Thanks!

 

It's probably either the alternator or the voltage regulator.

Jason

 

Check the Light Green/Red wire leading to the alternator. It is the "exciter" wire to turn on the alternator. This should be hot whenever the key is in the On/Run position. Mine had a pi**-poor crimp inside the weatherproof connector

 

i took it to napa a few days ago and had it tested, both battery and alternator test out fine, even under load. sometimes my radio wont play when i turn it on, i have to give the dash a small bumb and it'll kick on.
I also took the battery cable off while truck was running, it didn't die or drop idle or anything.
where's the voltage regulator located at on these trucks?

 

The Voltage Regulator is on the back of the alternator

 

Thanks guys, I took it off and had it rebuilt. I'll get it back tomorrow and should be good to go!