chilywily72

When driving if i press on the brake pedal to make the brake lights come on i can hear the fuel pump rpm come down, when i turn a blinker on the fuel pumps rpm goes up and down when the blinker goes on and off and when i put the emergecies on the voltage goes way down on the gauge and pulsates very high up and down would this be signs of a bad alternator? I was considering switching to the 3g setup would this be better im going to be running electric fans and i know i need the 3g alternator once i swap.

lxman1

Does this occur at just idle speeds or any rpm? Does it have underdrive pulleys? This will cause charging issues at idle speeds.

The 3G is a major improvement. I swapped mine over with a junkyard 3G alt. and it charges good at idle no matter what I have on, even the a/c, lights and electric fan.

Bubba 95SN

Some people have hearing like a animal, use ear plugs

dreamer1uk

Do a voltage drop test on the feed and ground side of the charging system circuit to see if you have excessive resistance anywhere

19stang88

DVOM, that will well you everything you need to know

Jfsram

No doubt, maybe another issue going on here. I can barely hear my pump with the engine off in the garage. While driving? That's either a loud pump or super hearing.

lxman1

Noisy pump is usually not a good sign. Mine got noisy while still under warranty and Ford replaced it. Might be a good time to go on and step up to a 155lph or even a 190lph pump.
A 155Lph pump will support over 400hp. and they are usually about 90 bucks.