Radio's

Have some friends who are Germans that lived here in the US for several years. Before they moved back to Germany they bought a new VW Passat here in the US. When they got home they found out that there car radio does not work. I believe it has to do with the radio frequency. Is there away they can change the US frequency to European frequency? Is it a computer download with a dealership or something else?

Nope, I think they’ll need to replace the radio.

I know I brought a Euro spec Blaupunkt AM/FM cassette from Switzerland and installed in it a 77 FORD and all worked well. What exactly does not work?

Broadcast AM and FM frequencies are pretty standard the world around. Satellite subscription radio is territory specific.

Twotone

The issue is that FM stations in the US end in odd numbers. (96.7, 102.5, …)
In much (all?) of Europe, they end in even numbers. (93.2)
US radios will only tune to the odd numbers. I have seen some aftermarket radios that will tune to both odd and even numbers. Maybe your Blaupunkt was like this?

A dealer will almost always say replace the radio, after all it’s what they know how to do. Your friends need to contact the manufacturer of the radio not VW. There may be something as simple as a jumper type connection that needs to be changed. Just an aside the Onkyo receiver right here on my desk will tune to both odd and even decimals.

If they do find they need to replace,they need to be careful - VWs use the radio as part of the car’s overall electronics system, I’ve read where replacing it with an aftermarket unit can cause problems.

It might not just be the frequency intervals. It could also be that Germany has switch to a digital signal. In any case, they should just replace the radio.