Disabled Radio

[Max Hoepli]

Hi all,

 

Started my car, and saw that radio did not turn on, had to take 15A fuse in
number 4 position out, plug fuse back in. inputted CODE into radio, after
which I could turn radio on.

 

Why did the radio become disabled after having left the car standing without
running for 7 days? This has only happened if the battery became such that
motor could not turn over.

 

 

1986 Type 44 Turbo Quattro, 311,000km

 

Max