A4 B5, BJ99 - Navigation no longer finds satellites, phone is muted

Hi!

Here's a problem I'm having with my A4 B5 (facelift model), manufactured in 1999.
Small navigation system (MFD), FIS (driver information system), Symphony (I) with Bose, Audi car phone (likely a rebranded Nokia), all included from the beginning.

Two mistakes:

The navigation system is reporting that it is finding 0 out of (presumably) 25 satellites. I suspect a short circuit or that the receiver on the roof (it's an Avant model) has been damaged. I recall that the positioning accuracy gradually deteriorated... this could indicate gradual wear and tear or corrosion.

2. The car phone still works, but I can only hear the other person very faintly (whether using the hands-free function or holding the handset to my ear). He seems to understand me pretty well, though.

Does anyone have any suggestions for me? For example, could I temporarily disconnect the phone's earpiece and see if the problem lies in the intermediate wiring? Are there any known issues with that?

Alternatively, can I perform a factory reset on the individual components? Undocumented features?

Regards,
Felix.

flaufer wrote:

... 1. The navigation device reports that it is finding 0 out of (presumably) 25 satellites. ...

He'll hardly find someone who is 25 years old.
Until about 3-4 years ago, 8-channel receivers were common, but since then, 12-channel receivers have become increasingly popular.
If he doesn't find anything, the antenna is usually defective. It's powered by a phantom power supply, and after a few years, the reception stops working. Just normal wear and tear.

I also think the antenna might be the culprit. It could probably explain both problems (navigation/phone).
In newer models, the antenna is diagnosable (via radio/navigation).