Test with a multimeter

DC fan (5 V, 40 mm)

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Now: Short circuit check: + to −

5 V CircuVanta 6000 counts · auto range DCAUTO•)))HOLDFUSE− HOLD LIGHT OFFV⎓V~Ω•)))FmA⎓ mA400 mACOMVΩ Positive supply (p) 1 p Negative supply (n) 2 n
Pin 1: Positive supply (p) (p) Pin 2: Negative supply (n) (n)

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 continuity.

Test setup: Setup: it powers the fan with 5 V; the multimeter is in series to measure current. Press the “Power on” button.

Measure step by step

A brushless fan has driver electronics inside; the Ω range cannot tell a good fan from a bad one, it only shows a short circuit. To decide, you power the fan with the setup and look at the current it draws. Do not connect the poles in reverse.

Do not touch the blades while the fan is spinning. The red wire is plus (+), the black one is minus (−).

  1. 1Short-circuit check: + and −
  2. 2Voltage when powered
  3. 3Current drawn when powered