99 A6 (AVANT) - BOSE CONCERT radio - LIGHTS UP BUT CAN ONLY HERE FAINT SOUND FROM REAR SPEAKER / WOOFER WHEN TURNED ALL THE WAY UP - ALL FACTORY SYSTEM. bEFORE THIS THE VOLUME / POWER **** DIDN'T ALWAYS RESPOND IMMEDIATLY TO VOLUME CHANGES

I took off the connections at the factory amp / bass tube and plugged it back in and the radio will worked for a few minutes thenthe volume will die again and I will only hear the faint sound of the base woofer. It does this each time i unplug it and reattach it

Any suggestions?