Wire colours in a computer fan

Written by ronald bell
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Wire colours in a computer fan
Colour-coded wiring can help you troubleshoot a computer fan. (Image by Loma Jefferies; Flickr.)

Small fans keep your desktop or laptop computer's internal temperature cool and stable. The fan's label indicates the amount of air flow, which is expressed in cubic metres per minute (CPM). Larger computer cases will have both an intake fan and an exhaust case fan. Colour coded wiring makes it easy to troubleshoot defective computer fans.

Wiring standards

International standards determine the pin-outs for interconnected components in PCs. There are only two standards for connecting the fans. The three-wire connection provides positive DC voltage, ground and fan speed. On the four-wire version, the fourth wire is for a speed control signal to the fan.

Three-wire connectors

The three-wire configuration includes a Molex connector to accommodate three wires. They are: black for ground, red for positive DC and yellow for the output tache from the fan. The tache line provides revolutions per minute (RPM) information back to the computer.

Four-wire connectors

Most computers use the four-wire configuration. This includes a fourth wire that provides a pulse width modulated (PWM) signal to the fan to control its speed. The fourth wire is usually blue.

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