Hi Scott, thanks very much for your help!
I've found a blue/yellow wire coming from the head unit that disappears down the back. When it re-emerges there is no blue/yellow wire but there is a purple/white wire that goes back to the pillar and is not connected to anything. Could that be the wire that is supposed to go to the amp?
I've recently acquired a 1995 Discovery 300tdi and decided to replace the non functioning stock head unit with a sony one. I've managed to connect it all up and it works fine apart from the rear speakers.
I've searched around for a fix and came across a cable that connects the black and red wires with a pink connector to an RCA port on the new head unit. Unfortunately it hasn't worked and theres no sound at all from the rear speakers.
I then found a forum post that said to connect the single RCA plug to a cable that has two RCA plugs to go into the head unit. This hasn't worked either.
In my frustration I plugged one of the rya plugs into a wire coming out of the head that says AMP REM which then made the rear speakers make some noise.
Does anyone know what I should do? Any help would be massively appreciated!