car wont start after upgrading to 0 guage??? please help

[jkrueger07 0]

Okay I just upgraded my 4 Guage to 0 gauge , me and my buddy both wired our cars, his car for some reason wouldn't start. He thought it was his battery, anyways my car worked fine, about 12 hrs later I go to start my car and it will not start, its not my battery, I checked it and its at about 12.5 volts, I unhooked the main source and still nothing, any ideas of what it could possibly be??? Sensors, relays, fuses etc.

[jonbearsmt 919]

check all fuses. under hood and under dash,

[Godsmack 360]

Check the wire for a cut and it grounding out too.

J

[Impious 1,476]

Was this just a power wire for amplifiers or a "Big 3" upgrade ?

[shizzzon 461]

explain exactly everything you did.