88 "EF" alternator possibly bad

[mikesEK]

PROBLEM SOLVED!!!!PLEASE DELETE!!!
1988 civic .............when car is revved up around 4500 5000rpm the battery light comes on ,I assumed the alternator is going bad and dropping in voltage ,but i hooked up a multi-meter and found out it when I rev up the car the voltage jumps to 17-18-19volts

my question is ..is there an external voltage regulator ((i don't think there is))that needs to be replaced or does the alt need to be replaced

next question....((i have 2or3 alternators lying around from d-series "EK" motors)) will "EK" alt work on the "EF" I figured they might swap because they're both D-series

Thanks in advanced guys...later