|ADVANCED TUTORIAL: This is an advanced tutorial. The following steps should only be performed by an advanced user. Improper or accidental changes to the system BIOS could permanently damage your system.|
If the CPU fan display in PC Health shows 0 RPM, it could indicate that the fan has failed. A failed fan leads quickly to CPU overheating, which can damage or destroy some processors, or cause those equipped with thermal monitoring to slow down to extremely low clock speeds. However, there are other conditions which can cause a CPU fan to display 0 RPM. See the following steps.
|The CPU fan connectors on typical motherboards are not designed to provide a great deal of power. They are adequate to power standard OEM-type heatsinks, but if the user has a high-powered or multifan heatsink, it might be powered by a four-pin connector from the power supply. If the connector does not have an adapter which can plug into the motherboard to provide fan speed information to the BIOS, the fan will appear to have failed.
|Most recent motherboards have two or three three-pin jacks used for powering and monitoring various fans. For example, the North Bridge (Memory Controller Hub) chip on many recent systems is cooled by a heatsink with a small fan plugged into the motherboard. Rear case fans are often connected to the motherboard. If the CPU is plugged into one of these jacks instead of the CPU fan socket, the CPU fan will report 0 RPM (if unused) or the speed of the fan plugged into it.
|A CPU fan which turns too slowly can also cause the CPU fan speed readout in PC Health to display 0 RPM. This happens when the fan speed falls below the minimum threshold for reporting. A heatsink with a fan which turns too slowly must be replaced immediately to avoid CPU damage from overheating. See the tutorial "Troubleshooting CPU Overheating" for details.
|A noisy CPU fan is an early sign of impending CPU fan failure; its bearings are no longer adequately lubricated or the fan is so dirty it cannot spin without making noise. Replace a noisy fan, even if it still provides adequate cooling, because it could seize up at any time and cause the CPU to overheat. A noisy North Bridge fan should also be replaced for the same reason. Keep in mind that the North Bridge chip, unlike the CPU, is not a socketed chip and cannot be replaced if it overheats. For details, see the tutorial "Troubleshooting the North Bridge."