Having problems w/intermittent radio.I have an 03 durango w/six disc changer - infinity system. Radio will work properly and then sound stops coming from spearkers. Appears radio is working properly, all lights are on and all functions appear tobe working, just intermittent sound. Think problem is in the amp, but not sure (Ican't get anyone to test amp, they just want to install a whole new system). Dodge tells me amp is about$160, but is a non returnable item??? Any help would begreatly appreciated - new to forum.