i have bin having issuse with the radio and mazda has replaced the hole face plate like 5 times already under warrenty. here is what the problem is it turns on and every thing but u get no sound or nothing not even the beep noise when u press the buttons and it looks like it works fine but no sound. but the radio works some times when i cycle the key on and off and it dose this with every radio they put in mazda says there is a short that would mean 5 of the radios they got were busted. also the amp in the trunk if that has a short in it it would make no sound come out of the speakers. to me it sound like it is a bad amp any thoughts?

it is a 05 and it has the bose system 6cd

The amp in the trunk only handles your rear speakers. You would still here something out of your fronts if it was the amp, unless it already damaged the HU. You would still get something at first though. When they replace your HU do they give you back your radio faceplate or have they replaced that as well? To me it would make sense that the Bose amps would be on a separate fuse. Maybe check and see if it is and if it is blown. Good luck