stereo cutting out

[jeffro788]

Got another one, I have put in several stereos in these trucks along with amps, speakers, and subs, but for some reason I can't figure this one out. Originally when i bought the truck it had an aftermarket stereo in it that I have now replaced with another aftermarket. When you turned up the radio between half and 3/4, it starts cutting out and gets worse the louder it goes. I have seen this when a vehicle is turned off b/c it is telling you the battery is dead, but this is while running and driving.
I meant to see if the previous owner put a fuse in that is too small and not allowing the proper current flow to power it. It does have the factory harness and I used the adapter and connected it to the radio harness, I have never had a problem doing it this way. Any suggestions?
This is on a 2000 chevy p/u.