How to Replace Door Sensors on Security Systems


Magnetically operated door sensors activate an alarm on commercial and residential security systems. The sensors consist of a door-mounted magnet and a switching device mounted on the door frame. When the security system is on and a door is opened, the switch contacts are removed from the magnetic field and the security circuit is closed which sets off the alarm. The system remains activated until it is disabled by the homeowner or other proper authority. You can replace the sensors with basic do-it-yourself ability.

Things You'll Need

  • Philips screwdriver
  • Flat-head screwdriver
  • Step ladder
  • Turn off the electrical supply for the alarm system.

  • Attach a sign on the entry side of the door you are working on to alert others of the work being done. If possible, route door traffic to an alternate entryway.

  • Locate the sensors that need to be replaced. Typically, the sensors are at the top leading edge of the door opposite the hinges.

  • Remove the two mounting screws from the wired sensor on the door frame using the appropriate screwdriver. Turn the screws counterclockwise and remove the sensor from the door frame. A step ladder may be required to reach the sensor.

  • Loosen the two terminal screws on the old sensor using a screwdriver.

  • Remove one of the two wires from the old sensor and connect it to the same terminal on the new sensor. Tighten the terminal screw clockwise with the screwdriver.

  • Connect the remaining wire from the old sensor to the other terminal on the new sensor and tighten the terminal screw.

  • Line up the mounting holes on the new sensor with the holes in the door frame. Insert the mounting screws and tighten both clockwise using a screwdriver.

  • Remove the magnetic sensor from the door. Turn the mounting screws on either side of the sensor counterclockwise using a screwdriver.

  • Install the new magnetic sensor onto the door. Line up the mounting holes and tighten the sensor screws.

  • Restore the power to the security system and remove the sign from the entry side of the door.

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