I have no audio sound coming from my radio, cd, satellite radio or casette player. The display shows that its receiving signals but I'm unable to hear anything. My husband checked the speakers and said they're fine. He thinks that its something electrical. A mechanic told me to just replace the entire unit (while repairing something else), but he didnt check the system at all so I dont want to purchase a new unit/pay installation cost if thats not in fact the problem.