Have No Power help!

i checked the fusable link at the firewall on the engine side and it had 12 volts. Can the link burn up without physical damage? I have 12 volts on both sides of the ammeter. Could it be the ammeter? How do i check to see what is wrong? How do i check the ignition switch? I just assumed it is the swtch cause before it sparked i had power and the car started just fine. Thanks for any help