What's the issue when headlights don't work on 2005 Chevrolet Trailblazer

My nephew put a new radio in, when he was finished, I had no headlights, the ac didn't blow out air and some other lights did not work as in the radio and inside lights.

by in Fayetteville, NC on September 08, 2013
1 answer
ANSWER by on September 10, 2013
The simple answer, and probably the issue, is CHECK YOUR FUSES. Then, if they are all good, you need to look at a wiring diagram and see what he "might" have tapped into.