I've searched the forums and can't seem to find a similar issue. The other day our 2002 C320 wagon wouldn't start. It was sitting for about a week without being driven and the battery had about 3 volts in it so something is/was seriously draining the charge and it isn't the seats (I've already been through that, one replaced and one unplugged).

Prior to this happening the radio stopped working and the screen on the radio just showed ---------- and the dash is blank for the audio portion. I had a new battery installed and the radio came back to life for a couple of minutes and then died again. I did a amp draw test by removing all the fuses one at a time in all three locations and really couldn't find any significant draws, the current draw when off is .03 amps which I believe is normal. If I pull the radio fuse or disconnect and reconnect the battery the radio will come back on for a few minutes and then die again.

Does this sound link a bad radio to you guys? Could this be the reason for the dead battery? It just doesn't feel right to me and I can't find another thread where a bad radio killed the battery. For now I have the radio fuse pulled just in case.

What radio is fitted? Does it have an audio gateway? Is there an amplifier? If there is no comms on Most bus the radio will power down after a few seconds

This is the stock radio, here is a pic below of the same one from the web. I'm not sure if it has an audio gateway or and amplifier, but there is something in the back passenger wheel well compartment (wagon, no trunk) that could be one or both of these things. I still have the fuse unplugged and so far no draining of the battery. But if its a bad radio, why do you think it comes back on when I unplug and reconnect power?

Does anyone know if I need a code for the replacement if I buy a used on off eBay?

No code needed as far as I know