I removed the becker radio from my friends 1989 300-E to send out for repair.
Not that I think the two are related, but this is what happened.
The keys I was given are the valet keys with out the red dot. Not that that makes any difference for what I was doing.

When I went to go lock the car with the square key drivers side front door. The factory horns alarm go off. The only way to lock the car was to walk over to the front passenger door push down the button so all the vacuum locks ingage and close the door.

What should I check? Could a loose wire from the factory radio be the problem or set this alarm in motion when I used the drivers door and lock ?

Any help would be appreciated.

Bob Geco