There are no shortcuts in finding this fault. If you have already checked whether the fuse is OK in the fusebox , then the only thing to do is to remove the radio and see if it works by wiring it up on the bench( Battery +/- plus speakers) ..Alternatively substitute it for another radio. . This will prove whether it is the radio or not. If the radio works OK on the bench , then the fault is in the car wiring and will have to be checked using a multi-meter or test lamp....Good Luck
RegWorts
May 2008