If one’s house alarm or car alarm goes off on Shabbat, is it permissible to ask a gentile to turn off the alarm?
Generally speaking, "Amira Le’akum" – asking a gentile to perform activity that is forbidden for Jews on Shabbat – is forbidden on Shabbat by force of Rabbinic enactment. One may not ask a gentile to do on Shabbat anything that a Jew may not do on Shabbat. The Sages did, however, make several exceptions to this rule under certain circumstances, and each situation must be assessed individually to determine whether it falls under the prohibition of "Amira Le’akum."
Regarding the case of an alarm, Hacham Ovadia Yosef rules (as cited in Yalkut Yosef) that one may ask a gentile to turn off a house alarm or car alarm on Shabbat. The alarm disturbs the people in the neighborhood, including sick patients who may be unable to sleep, and could potentially cause a Hillul Hashem (desecration of God’s Name), and these concerns override the Rabbinic prohibition of "Amira Le’akum." One may thus show a gentile the button to press and explicitly ask him to shut the alarm. This applies even if the gentile will turn on a light in the process of shutting the alarm, such as if he must enter the car. The Jew’s request relates specifically to shutting the alarm, which entails only a Rabbinic prohibition (stopping an electric current), and the Torah prohibition of turning on lights occurs only as a byproduct of the primary action. One may therefore ask the gentile to turn off the alarm even if the gentile will turn on a light in the process.
Of course, if the alarm will turn itself off after a minute or two, then one should simply wait for this to happen, rather than asking a gentile to turn off the alarm. Our discussion here concerns those alarm systems that sound a siren indefinitely until the system is turned off.
Summary: If one’s car alarm or house alarm sounds on Shabbat, one may ask a gentile to turn it off. If the alarm will turn off automatically after just a couple of minutes, then one should simply wait for the alarm to turn itself off.
