Recently I've been noticing a very intermittent voltage regulator problem. I'll be driving along at night and my lights will dim, stereo will get quieter all for just maybe 20 seconds and without changing anything the voltage will come back up. It looks like the voltage will go down to probably 10volts or so before it comes back up to the normal 14. Also the part I really don't understand is that it will only happen about 10-15miles into a drive I've never noticed it on a short drive so anyone have any ideas on how to fix it without replacing the alternator.

 

The most common problem with alternators.
https://www.ranger-forums.com/showth...hlight=brushes

 

Ah alright thanks, I searched about alternator issues but never found that.