Try a Hard reset.
When I changed my alternator out, I had no radio at all. The display lit up but no actual frequency numbers no sound, nothing .
A hard reset resolved all but I do not know why and there was no good reason why an alternator replacement should affect the radio either.
The good news is a hard reset costs nothing, does not harm anything and does not do much either, but sometimes it resolves problems.
After the hard reset, you will have to reset the clock on the radio but the station presets still remain after a hard reset.
Also there is a
sound level increases with speed feature, Automatic Volume Control, AVC . Trying turning it off before you do the hard reset.
You push and hold the tone switch, (button to the left of the volume knob), in for about five seconds and the display will now hopefully display the speed volume numbers, 0 to 9. Rotate it counterclockwise so the numbers show zero. This means AVC is off. Maybe that will solve the problem but I doubt it so then try the hard reset.
The hard reset instructions are below.
In brief, to start the hard reset process, open the hood but close all doors and let your 3 go to sleep - no radio display etc and no key in the ignition. This will take a couple of minutes and do not open any doors until the reset is completed. (I find that it is often a good idea to have the drivers door window rolled down and the key in my pocket whenever fooling about the vehicle.) Also when I play with a car battery, I remove any rings I have from my fingers, also my watch.
Disconnect the ground battery terminal from the main starting battery.
Disconnect the positive battery terminal from the main starting battery.
The reason for this order is if a wrench or loose battery cable ends grounds to the body, no arcing or other bad things happen.
(I assume that you only have one battery in your 3. If not, disconnect the others as well and leave them disconnected until after all is done.)
Connect the negative cable to the positive cable. (NOT the battery.) You will need a short length, (a foot or so), of light gauge, (14 to 18 gauge AWG, insulated stranded copper), wire to span between the battery cable ends as there is not enough slack in the positive and negative battery cables for the ends to touch each other.
Hold all together for about a minute or more, (at least two minutes), as you are discharging memory modules within the engine computer and elsewhere. Then it is suggested you then just let all sit disconnected for say ten minutes, (minimum five minutes), prior to commencing to put the battery cable ends back on the battery posts per the following order.
Reattach positive terminal to the main starting battery positive post.
Reattach negative terminal to the main starting battery negative post.
Start engine and hopefully none or at least fewer warning lights.
Reset time on the radio - note that the station presets are still there as not everything is erased. Nothing much else needs resetting either.
You can also now connect up the other batteries if you have a multiple battery setup.
This is a link to a thread in disco3 re the hard reset procedure.
http://bit.ly/14WXXR1
This is a link to a thread on Disco3Club re the hard reset procedure.
http://www.disco3club.co.uk/phpbb/viewtopic.php?f=67&t=3374
