I have an OEM Navigation system (Mk4) which was working until we had some flat battery trouble. Now we have a blank screen.
From what I hear the old Mk3 firmware's were susceptible to voltage spikes and jump-starting could kill them.
We now have a blank (but backlit screen). The radio works fine, and you can still operate the channels, even select TV (audio only) but no picture. I don't know my way through the menus well enough blind to get voice prompts see if the GPS is still working.
I've tried swapping back to the MK3 but that didn't work either which lead me to believe that perhaps it wasn't the computer.
Our local BMW Dealership diagnosed the "Head Unit" (display). So I replaced that with a working (I was assured) unit from ebay but it's exactly the same problem.
I've tried putting a V29 firmware CD into the computer because I understand that it will eject when it finishes and that might fix a problem with the computer flash. I've done that, but nothing visible still. The eject button works OK, the light comes on, it whirrs into life but I don't get a picture.

I'm forced to conclude one of three things;
1) The dealership misdiagnosed the fault - it isn't the head unit after all.
2) The 'new' replacement head unit/display has the exact same fault as my unit and was sold to me by a scammer.
3) I broke something else putting in the display (unlikely).

Does anyone have any other ideas, or recommend where I might be able to get it fixed?

I now have two computers, a MK3 and MK4 and two head units. The navigation doesn't work with any combination. Presumably if BMW didn’t quote the GPS as being at fault they’ve managed to ‘talk’ to it over the iBus successfully?