It could very well be a fader related problem.

To check if the wires you've used are the ones you thought they were you can test that the speakers work by connecting them to a 1.5V battery - click say the +tve connection on and off the battery and listen out for a click at the speaker.

With a modern radio it is best just to either extend the rear speaker wires from the fader or put in new wire as the mercerator (thayer) said.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!