Within two days of one another my '86 300SDL and '87 560SEL, alarm systems have gone nuts. Same problem both cars. Doors locked, system operates, umlock either front door or trunk and the alarm sounds continuosly. Alarm system cannot seem to be disarmed. Only remedy is to remove the fuse, which renders several other systems non-functional. Any ideas as to what's going on?


'86 300SDL 202,000
'87 560SEL 126,000

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jcciem
'94 SL5000 60,000
'91 350SDL 545,000
'91 350SD 197,000
'00 E55 AMG 77,000

Can you disarm the alarm by unlocking the passenger door or trunk? If so then you probably have a bad alarm switch in the door handle mechanism. As I understand you can't replace just the switch - you have to replace the lock or handle mechanism (not sure which). Try this - unlock the car, pull the door open, quickly twist the key to lock. That's how I dealt with my 91 300SE until I realized that no one was going to steal it and disconnected the alarm. To do so, pull either of the 14(?) pin connectors into the long slim box behind the plastic panel in the passenger footwell. IIRC, the box is marked Becker Autosound or something like that.

Sixto
95 S420
87 300SDL