Why Isn't My Wired Door Sensor Working?

A wired door sensor may not show the correct status on the system due to a wiring issue like incorrect End of Line Resistor placement, faulty programming or a combination of these problems. In order to determine the source of the issue, all of these potential problems must be considered.

Make the following checks to determine the cause of your faulty door sensor:

  1. Check the programming. Modern hard-wired panels, such as the Vista-20P and the Vista-21iP, offer the option for supervising zone wire with an End of Line Resistor. However, this is not required. Zones 2 - 8 can be programmed as Normally Closed, Normally Open, EOL, Zone-Doubled or Double-Balanced. Zone 1 must always use a 2000 Ohm (2K) resistor. Most burglary devices are Normally Closed, meaning when they are activated, or faulted, they are open, but in their normal state, they are closed. Make sure that the programming for the zone matches the contact and wiring option you decide to use.
  2. Check the wiring. On zone 1, make sure a 2K resistor is installed in the zone. For Normally Closed devices, the resistor should go in series, while Normally Open devices will need to have the resistor go in parallel. End of Line Resistor means that if you wish to supervise the wire run, then the resistor should be installed at the last device on the zone. Resistors installed at the alarm panel are ineffective, and they might as well be omitted from the loop on any zones that allow for programming without a resistor. If resistors are not going to be used, make sure to program the zone as either Normally Open or Normally Closed based on the contact(s) that are being used.

  3. Test each device. Once programming and wiring have both been completed, test each device. When all of the doors on a zone are closed, there should be no fault displayed at the panel for that zone. If any door on the zone is opened, a fault for that zone should appear.

  4. Troubleshoot any issues. If the door zone doesn't behave as expected, check the following:

    1. Does the zone show a fault when all contacts are closed? Check programming to see if a resistor is expected by the panel for the zone. If it is, make sure that the resistor is present, is the correct value and that it is properly placed based on the normal state of the zone.

      If the zone is not expecting a resistor, make sure that it is programmed for the correct "Normal" position. If you program the zone as Normally Open and you use Normally Closed contacts, the zone will display as faulted when all the doors are closed, and as normal when any door is open.

      If programming and wiring both check out, make sure that the gap spacing for the contact and its magnet has not been exceeded. For example, the Honeywell 949 surface mount magnetic contact allows for a gap of up to 1.25 inches. If the magnet is more than 1.25 inches from the contact, the door will be seen as open, even if it is closed. Gap spacing varies per contact and magnet, so make sure to check for proper spacing for the type of contact being used.
    2. Does the zone never show a fault? This is a rare occurrence, and for this to happen, there is most likely a wiring issue.

      If the zone is programmed for end of line resistor (and assuming zone doubling is not in use), this could happen if the 2K resistor is strapped across the zone terminals and there exists a break in the wire going to the door contact(s). This will prevent the panel from ever seeing a short on the zone. If it never sees a short, it will always see the resistor, and it will never display a fault condition

      If the zone is programmed for Normally Closed, and there is a short in the wiring somewhere between the first contact and the panel's zone terminals, the short will always be seen, and a fault will never be displayed for the zone.

      By the same token, if the zone is programmed as Normally Open, and there is a break in the wire between the zone terminals and the first device on the loop, a fault will never be displayed. This is because the panel will always see the zone as open, which is what it sees as the normal condition of the zone.

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