I"m helping a buddy put his gsr swap in his EM1 thats been sitting with a blown b16 for the last year this weekend and I'm trying to figure out the electrical issue he was having.

So he was jumping the car to pull it out of the garage and accidentally hooked up the terminals backwards. I guess some sparks flew and he took it off right away and switched them. Car started normally and drove but when he turned his headlights on the speakers lost all sound but the deck is still on and looks like its functioning.

I am a complete noob when it comes to wiring so help would be great. Where should I start to fix this? Anyone else had a similar situation?

Thanks guys.