I have just installed a new kenwood H\U in the wifes hyundai and all was good until I tried to tune it to the fm modulator for the stacker and now there is no sound. I checked all the wiring for a short some where, all good. The joints were all soldered. The unit still powers up ok and does everything it should but no sound, I wired up another speaker and checked the seperate outputs and still no sound. Could the stacker unit be faulty and damaged something or should I be looking some where else.