runs rough when alternator plugged in

[urban_assult450]

i have a 90 ranger 2.3 and for some reason when the alternator is plugged in the truck runs horrible and when unplugged it runs like a top, changed alternator with one from salvage yard and it didnt fix it. so any ideas to help would be great

p.s. dont know anything about rangers only had couple days

 

[martin]

Check what voltage you get when the alternator is plugged in.

 

[urban_assult450]

14.7 volts when plugged in and all grounds tested as perfect and oh its rund leans for some reason too cuz i checked the plugs

 

[Bob Ayers]

It sounds like the plug wires are breaking down with the higher voltage, which you will get by raising the battery voltage.