any help on this matter would be GREAT!!! my original problem started a couple of months ago with crackling and popping speakers - volume wouldn't go up, etc. anyway i found another used replacemeny w140 bose amp. got it in the mail last week - installed it and whatdoyaknow - same problem. the guy i bought it from swears it worked when he took it out - he put a new system in his w140 500 sel. is there any chance the the head unit could be the root of this problem or perhaps he knew it was defective and went ahead and installed a new system because of it. i am in the process of contacting paypal and my credit card company (mbna) to see what my options are. any ideas? thanks!!