Test with a multimeter

Relay

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Now: Coil resistance (A1-A2)

5 V CircuVanta 6000 counts · auto range DCAUTO•)))HOLDFUSE− HOLD LIGHT OFFV⎓V~Ω•)))FmA⎓ mA400 mACOMVΩ Coil terminal 1 1 A1 Coil terminal 2 2 A2 Common contact 3 COM Normally open 4 NO Normally closed 5 NC
Pin 1: Coil terminal 1 (A1) Pin 2: Coil terminal 2 (A2) Pin 3: Common contact (COM) Pin 4: Normally open (NO) Pin 5: Normally closed (NC)

Red probe Not connectedBlack probe Not connected

Hold the probe and drag it to the tip of a leg. Tapping works too: first pick the probe, then the leg.

Set the range to Ω (resistance).

Measure step by step

A relay has two separate circuits: the coil and the contacts. First measure the coil in the Ω range, then find in the continuity range which contact COM is connected to, and finally apply voltage to the coil and watch the contact switch.

Take the measurements with the relay out of the circuit. Apply only the voltage on its label to the coil; don’t touch the mains side.

  1. 1Coil resistance (A1-A2)
  2. 2COM to NC: connected at rest
  3. 3COM to NO: open at rest
  4. 4Apply 5 V to the coil, COM to NO