Using a Multimeter to Test your Wired Zones

Checking the integrity of your wired contact sensor zones will ensure that the zones can be connected to the Retrofit Alarm Kit. Wired contact sensor zones must create a complete closed loop in order to work properly with Retrofit Alarm Kit.

Before you begin this step, check that all doors and windows are closed. To test your contact sensor zone using a continuity tester or multimeter:

A. Identify which zones are contact sensor zones using the alarm diagram.

B. Remove one contact zone (2 wires) from your wired alarm panel.

C. Turn on your multimeter and set it to measure resistance.

D. Wrap one end of the exposed zone wire around one of the testing probes.


E. Wrap the other zone wire around the other probe.

  • If the zone test is successful, the continuity tester will show a number. (This number will vary based on the specific resistance of your system.) Congrats! This zone can be successfully wired to the Retrofit Alarm Kit.
  • If the zone test failed, the tester will show the number 0 or a very low number. If the multimeter has a very low resistance reading of less than a few Ohms, it’s probably missing the end of line resistor. This means that the zone is missing an end of line resistor or is not working, and it can’t be wired to your Retrofit Alarm Kit.
  • If the zone test shows the letters OL or Open Loop, the zone is open. Check that all doors and windows in your home are closed. If everything is closed, there is no visible damage to the wiring or sensors, and the tester still reads OL, then there is an issue within that zone that needs to be diagnosed and repaired. If not repaired, this zone can’t be added to the Retrofit Alarm Kit.

If any of your zones fail the integrity test, we recommend that you hire a professional alarm installer to repair the zone. Failures can be difficult to diagnose and may have a variety of causes, including:

  • The contact sensor hardware has been damaged.
  • The wire is no longer connected to the sensor.
  • The wiring inside the wall is broken or disconnected.

The Retrofit Alarm Kit will not work with wired zones that fail an integrity test. If you cannot repair the wiring for a zone, wireless Ring Alarm Contact Sensors can be used to secure the doors and windows in that zone instead.

Which wired alarm zones are compatible with the Retrofit Alarm Kit? Click here to find out.


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