I have a 2007 Grand Voyager with a REK AM/FM Stereo Radio with cd player. The head unit lights up, accepts CDs and all functions seem to operate but with one problem - no sound at all. I was told it was the head unit that had gone so purchased a ISO conversion harness with a view to installing an after market head unit. Installed it with an old head unit that I had, which I knew worked, but with exactly the same results as the dealer fitted head unit. I suspect the head unit is OK but something is wrong between the head and the speakers. Is there an amp in the system somewhere or fuses that I can check?. (excluding those under the hood as they seem to be OK)