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Testing a magnetic door or lid sensor: reed switch (2 wires, no power) vs Hall sensor (3 wires, powered)

Magnet-operated door and lid sensors come in two kinds. A reed switch is a pair of contacts sealed in a small glass tube; it needs no power and simply opens or closes when a magnet comes near, so you test it with a meter on continuity. A Hall-effect sensor is an electronic chip that needs a supply voltage and gives a signal output, usually with three wires; you test it powered (supply, ground, signal). Identifying which one you have first saves a wrong part and a wrong test.

Cross-checked ~15 min easyBrands: All

Before you start

  • Unplug the unit before disconnecting the sensor
  • Powered Hall-sensor checks are done with the unit on; probe only the low-voltage sensor connector

Diagnostic steps

Unlock all 5 steps with expected values

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

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Testing a magnetic door or lid sensor: reed switch (2 wires, no power) vs Hall sensor (3 wires, powered) · OnCall Tech