2000 mercedes s430, no volume

I have a freind. Like me who does installs on the side. He took on a job that even I dont mess with.... Mercedes, 2000 s430.. bose system and navigation... cd changer and factory amp is located in the trunk along with the battery. Here is our delemna. I am now employed to fix his mess.. he used a testlight to figure out the amp turn on wire. and tagged an loc on the speakers themselves. given that this is a bose systme im sure that was a huge no no. now he has no volume in the whole car. nothing. please help asap. need this car out of my driveway soon. plus the guy he is working for is a brick and i have turned down his jobs before. please help me get him off his back. and get this car done. give me tips on what to look for. it is raining tonight so after work tomorrow i hope to get a fresh start on this. any help would be most appreciated.If you cant here it a block away then I didnt do it....

Using a meter check voltage on the amp.  It may be as simple as a blown fuse.  There should be some larger wires for power and ground.  There should be some smaller wires for input and remote turn on.  Medium size wires for speaker output.  There is a good chance that the test light took out the turn on wire from the deck.   Notice I said using a meter.

thats what i usually use... i did check the fuse.. it is not popped..... it is easily accessable it is towards the top of the amp when you lift the carpet in he trunk....If you cant here it a block away then I didnt do it....

one more thin.. it also shows no d changer on the screenwhen i go to select cd...If you cant here it a block away then I didnt do it....

Did you use the meter to see if there was 12 volts on the fuse of the amp?  The changer and the amp may get power from the same source. 

i remember there being a secondary fused distribution block underneath the backseats... u may find your blown fuse there.....there can be only one.......