220-1101 Question 298
Single answerFansA technician is troubleshooting a desktop PC that has started shutting down unexpectedly after 10 to 15 minutes of use. The user reports that the system becomes very loud just before it powers off. In the BIOS/UEFI hardware monitor, the CPU temperature rises rapidly, but the CPU fan speed reads 0 RPM even though the technician can see the fan attempting to spin intermittently. The heatsink is properly seated. Which of the following is the BEST next step to resolve the issue?
- A
Replace the power supply because unexpected shutdowns usually indicate insufficient wattage
- B
Reconnect or replace the CPU fan and ensure it is attached to the motherboard's CPU_FAN header
- C
Apply additional thermal paste on top of the existing paste to improve heat transfer
- D
Disable thermal monitoring in BIOS/UEFI so the system will not shut down during use
Show answer and explanation
Correct answer: B
Explanation
This question tests practical troubleshooting of fan-related overheating in a desktop system. The most important clues are the rapid temperature increase, the CPU fan speed reading of 0 RPM, and the fan only spinning intermittently. In real-world service, a technician should first confirm that the CPU cooler fan is connected to the correct motherboard header, typically labeled CPU_FAN, because many motherboards use that header to monitor tachometer signals and may trigger warnings or shutdowns when no valid fan speed is detected. If the connection is correct and the fan still does not operate reliably, replacing the fan is the appropriate fix. This aligns with standard PC hardware best practices: verify the cooling fan, confirm proper header connection, and do not disable thermal safeguards. Motherboard and system documentation commonly notes the importance of the CPU_FAN header for fan monitoring and protection features.
- A. Incorrect.
This is incorrect. A failing or undersized power supply can cause shutdowns, but the scenario specifically points to overheating: rapidly rising CPU temperature, loud operation, and a CPU fan reading of 0 RPM. Those symptoms more directly indicate a CPU cooling problem rather than a power-capacity issue.
- B. Correct.
This is correct. The BIOS/UEFI reporting 0 RPM for the CPU fan, combined with intermittent spinning and rapid CPU overheating, strongly suggests the CPU fan is not properly connected, is connected to the wrong header, or is failing. Best practice is to verify the fan is connected to the dedicated CPU_FAN header so the motherboard can monitor RPM and control fan operation. If the fan is defective, it should be replaced.
- C. Incorrect.
This is incorrect. Thermal paste should not be applied on top of existing paste. Old compound should be cleaned off and new paste applied correctly if repasting is needed. In this scenario, the heatsink is already properly seated, and the stronger clue is the nonfunctional or improperly connected CPU fan, not poor thermal compound application.
- D. Incorrect.
This is incorrect. Disabling thermal monitoring is unsafe and not a valid repair. Thermal protection exists to prevent CPU damage from overheating. Bypassing that safeguard could lead to hardware failure and does not address the underlying fan problem.