Windstar Anti-Theft Alarm Issue

It sounds like you're describing a potential issue with the alarm control unit. A malfunctioning alarm system can sometimes be triggered by low voltage or power failure. Has the battery been checked recently, or has there been any noticeable electrical issue prior to this alarm problem?

Thank you for the reply. Battery health seems fine; voltage is within the normal range. I recall reading something about the immobilizer possibly being involved. Is there any chance that this is related and do you know how to proceed?

It's possible the immobilizer may be a factor, but it's less common given the symptoms you described initially. Given that you are seeing error codes in the system and it is coded to optical locking with your indicators and that the battery seems good, it might be best to have a professional workshop take a look. The alarm control system is complex and often requires specialized diagnostic equipment.

Appreciate your help and insights. I took it to a shop; you were right, the alarm system was indeed the culprit. Turns out, the alarm system coding was faulty and triggering false alarms. The repair involved recoding the alarm control, with a final cost of 45€. Problem solved. Thank you again.