91 accord CC only works w/ headlights off

I have a friend with a 91 (or around that year) 4 door Honda Accord. He told me that after he installed speakers in the back, the 3rd brake light (the high mounted brake light inside the car) is always on (as if he were braking), and the cruise controls only work when his headlights are off. Any ideas? I can't figure it out, just seeing if anyone has ran into anything like this. Thanks in advance for any input.

It sounds as though he has messed up the wiring for the taillamps. Check for a disconected plug or ground wire. He may have also shorted the wiring for the brake lamp circuit somewhere. Begin by tracing all the wiring close to where he was working. Just replacing the speakers shouldn't make locating the problem too difficult. Retrace all the steps taken in replacing the speakers and you will most likely find the problem. sparky