My rear speakers stopped working a long time ago and I was wondering why, I can't see what is wrong. Just recently the front ones stopped working too, a mechanic replaced a fuse and the fronts started working just fine again, but still no rear. I don't understand how there is a fuse for the fronts, is there one for the rears too? Is there an amplifier in the car somewhere? I haven't made any modifications at all. Please help. Thank you.