Mercedes: radio alarm, high pitch tone, mercedes forum

Question
1994 Mercedes 350s- After entering radio code all was well until next time I started the car. Now the radio alarm (high pitch tone) stays on for 5-10 minutes before shutting off. Any suggestions for resolve?

Answer
Richard,
Have you tried to re-enter the code? Is this an after market or blau plunk German unit.  If yes an the problem persist, I would try this first.
Shut off all accessories including the radio.  Disconnect the battery terminals (-) first then positive (+). Wait 30 minutes reconnect the terminals (+) first then (-).
Start the vehicle then turn on the radio.
If you still have the problem I would contact a mercedes forum on the internet an post the question.
Good Luck
Rob