Ignition from box has a short

I was changeing speakers off my 84 cutlass and
out of no were after i was done and i wemt to turn
on the car with the ignitiom on , there was no lights
on the dash but car will start....when running i turn
on the lights it starts making that beeping noise as
if the car was off and lights were on..????wtf??? So
i have  a short somewere but idk where to start....
Battery is new alternator is new new light
switch.....but wats more weird  is when i turn off
the car the check emgine light will turn on for a sec
and shutoff...i tested the fuze box with a test light
all the fuzes get good power but the ignition
section that u can add a wire into it the power is
very low....what could be my problem....was going
to change the wire from the alternater to the fuze
box