What connector details must match in a fan replacement?

Verify five connector items before approving a replacement: pin pitch, pinout order, latch/lock geometry, wire gauge and length, and the mating connector part number. Same pitch with a different pinout is the classic trap — the fan runs perfectly on the bench with hand-jumpered leads and cannot be plugged into production hosts at all.

The five items

Pitch (2.0, 2.54, 3.0 and 5.08 mm families cover most DC fans), pinout order (power, ground, tach, PWM or alarm vary by maker), latch (friction fit vs positive lock — production lines need the latch), wire gauge (affects current rating and connector housing choice) and the mating part. Ask for the manufacturer's mating-connector drawing, not a photo.

Wire-in vs connectorised, and pin 1 discipline

For lead-wire (bare wire) fans, the equivalent checks are length, colour code, strip/tin dimensions and any sleeving or shielding requirement. Colour conventions differ between makers, so never rely on colour alone — verify by continuity on a sample. On connectorised fans, document pin 1 marking on both ends and check latch engagement force on a production fixture.

• For lead-wire fans, confirm wire length, stripping and tinning spec, and any sleeving.
• Mark pin 1 on both the fan lead and the host header drawing.
• If pinouts must differ, specify a custom wire harness — cheaper than a field recall.

When the connector cannot match

If the ideal electrical candidate ships a different connector, a custom harness or a custom fan lead is usually the cheapest resolution — far cheaper than re-qualifying a worse electrical match. Provide the host-side mating drawing and the required wire exit direction (side/top) when you request samples; both are standard customisation items and do not require tooling-level changes.