Under hard load, like around 4800rpm, my electrical system gets pissed off. at 5000rpm the battery light starts flashing and the lights begin to dim.

Granted, with my current program, it nevers see's this rpm under actual use, only during some blower testing I was doing. I managed to achieve 9psi at about 5200rpm with a powerdyne bd-11a and a 2.75" pulley.

 

im running 8lbs with no such problem could the belt be slipping?
https://www.f150online.com/galleries...w.cfm?num=9331

 

98Navi,
I had the same symptoms not too long ago. My battery light would flash a little then come on at about 4800 RPM. I had a NAPA lifetime guaranteed alternator. I took it to them and it was replaced. It was only putting out about 12.4 volts and less at higher rpm. They are supposed to put out 14+ volts.
This is an early warning that you will soon need a new alternator.

 

I blieve what I have is the 160 amp version. The 99 and up have a 200 amp version, think i'll upgrade it.