I have a 1973 4.5 W108, It has a Becker Mexico Cassette, I don't think that came with this car. But it not working. I was going to put a new radio in it, I notice the power black wire had no power I think it should have power when the key is on so. still no power, I check the Fuse in the engine compartment on the firewall, I believe the first fuse for the radio and other stuff put a test light, I have power their with the key on. were can I trace this Wire. I have did a search on some threads still no help.

Thanks to All replies
Eddie