The system fan is not spinning or not spinning properly.
The temperature inside the case is too high and the fan cannot spin fast enough to remove the heat.
HP Customer Support
HP Notebook PCs - System Fan (90b) error message on startup
This document pertains to HP and Compaq notebook PCs.
When starting the computer, the following error appears on the screen:
The system has detected that a cooling fan is not operating correctly.
Continued operation is not recommended and may cause unpredictable behavior that could result in random shutdown, data loss or possible system damage. The system will shut down in 15 seconds. To prevent shutdown and continue operation, press the Enter key now.
System Fan (90b)
In addition to this error, the system fan may spin faster and become louder.
This error indicates that a problem exists related to the heat removal system. One of two possible events is occurring:
This error message occurs to help prevent costly damage to the computer.
To fix this error, use the following steps:
If you notice that the system fan spins and is blowing warm air from the computer, clean the exterior vents to remove dust buildup by blowing air through the vent openings. Do this while the computer is off. Dust can accumulate inside the vent opening and around internal cooling components, preventing the removal of heat. After dust has been removed, try turning on the computer to see if the error goes away. if not, continue to the next step.For more information on reducing heat inside your computer, see Reducing Heat Inside the PC.
Perform a hard reset. Performing a hard reset can reset recorded thermal values in memory and enable you to use the computer again — even if only for a short time to access and save any important files before service. For information on performing a hard reset, see Use Hard Reset to Resolve Hardware and Software Issues.
In some cases, updating the BIOS may help prevent this error from occurring. For information on how to update your BIOS, see Updating the BIOS.
Have the computer serviced to clean internal components and replace the system fan if necessary. Ensure that the following items are addressed during servicing:
Thoroughly remove dust from all internal cooling components.
Ensure that wires from the system and CPU fans are connected to the motherboard securely.
Ensure that the system fan blades spin correctly, and that the fan is not producing loud noises. If not working correctly, replace the system fan.
Remove old thermal compound from integrated circuits and heat sinks, and replace with new thermal compound.
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