hi guys. When i brought my 2001 discovery the previous owner had a after market radio fitted. He removed it and replaced it with a lr one but didn't have the code. I've managed to get the code from lr and radio lights up fine but no sound. I've put 3 discs in the cd changer and radio says no disc. Is the head unit foobar. Cheers Mark.

Maybe, but maybe just an iffy connection at the rear of the headunit.

In most cases the output from "aftermarket" radio units is a high level designed to drive loudspeakers, whereas the output from the LR mid and hi-line radio head units is a low power level designed to drive the input to an amplifier, that's the unit under the passenger's seat.

IMO you're going to have the check carefully all of the wiring at the back of the head unit to make sure that it matches that which is required for your particular head unit/amplifier set-up.