Computer Shuts Down with Thermal Event: Fans Spinning but Overheating
A user reports that their desktop computer shuts down unexpectedly after about 30 minutes of use. The technician reads CPU temperature sensors in BIOS and sees the CPU idles at 45°C but quickly rises to 95°C under load before the system shuts down. The heatsink fan is spinning. Which of the following is the most likely cause?
⚠ Common exam trap
CompTIA often tests the misconception that a spinning fan guarantees adequate cooling, but the trap here is that the fan can be functional while the thermal interface material has failed, causing the CPU to overheat under load.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The thermal paste between CPU and heatsink has dried out.
The CPU idles at 45°C but quickly spikes to 95°C under load, triggering a thermal shutdown. Since the heatsink fan is spinning, the most likely cause is degraded thermal paste, which has lost its ability to efficiently transfer heat from the CPU die to the heatsink, leading to rapid overheating even with active cooling.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The thermal paste between CPU and heatsink has dried out.
Why this is correct
Dried thermal paste creates microscopic air gaps between the CPU IHS and the heatsink base, dramatically reducing thermal conductivity. Even though the fan spins at full speed, heat cannot be transferred away efficiently, so the CPU core temperature climbs to thermal limits. The motherboard's thermal protection triggers an abrupt shutdown to prevent silicon damage. This is the classic signature of degraded thermal interface material after years of use.
- ✗
The power supply is failing.
Why it's wrong here
A failing power supply can indeed cause random shutdowns, but it fails from ripple, load sag, or OCP/OVP trips; these occur instantaneously and without a gradual rise in CPU temperature. As the PSU loses regulation, the system typically resets or powers off abruptly, but the CPU heatsink/thermal solution isn't impacted by the supply's condition. The observed pattern — CPU temp steadily rising to 95°C over roughly 30 minutes — points to the cooling system, not the input power source. Measuring PSU rails with a multimeter would show normal voltages during the pre-shutdown window.
When this WOULD be correct
A desktop shuts down randomly under load, but CPU temperatures are normal (e.g., 60°C under load). The PSU fan is noisy or stops spinning, and the system fails to power on after shutdown. This indicates a failing PSU.
- ✗
The RAM has a timing error.
Why it's wrong here
RAM timing errors stem from unstable command or data line timings, typically producing data corruption, application crashes, or a blue screen (BSOD). They do not generate significant heat in the CPU, because the processor is not doing more work — it's just receiving bad data. A shutdown after 30 minutes accompanied by a CPU temperature reading of 95°C reflects a cooling path failure, not a memory subsystem defect. You would expect an immediate reboot or fault rather than a reproducible thermal trip.
- ✗
The motherboard VRM is overheating.
Why it's wrong here
VRM (voltage regulator module) overheating is a protection event, not a CPU heat event; the MOSFETs overheat due to high current or poor airflow near the socket, triggering the board's OTP (over-temperature protection) to cut power. That would protect the CPU but the CPU die temperature itself would not necessarily climb to 95°C — in this scenario the technician observed the CPU temp sensor rising, not the VRM sensor. A VRM fault usually causes sudden shutdown under load without a slow temperature rise across the CPU. Also, dried thermal paste is far more common and matches the timing of the symptom.
When this WOULD be correct
A question where a computer shuts down under load, but CPU temperature is normal (e.g., 60°C), and the VRM area on the motherboard is hot to the touch or has visible damage. The correct answer would be 'Motherboard VRM is overheating' due to inadequate cooling or failed VRM components.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓The thermal paste between CPU and heatsink has dried out.Correct answer▾
Why this is correct
Dried thermal paste creates microscopic air gaps between the CPU IHS and the heatsink base, dramatically reducing thermal conductivity. Even though the fan spins at full speed, heat cannot be transferred away efficiently, so the CPU core temperature climbs to thermal limits. The motherboard's thermal protection triggers an abrupt shutdown to prevent silicon damage. This is the classic signature of degraded thermal interface material after years of use.
✗The power supply is failing.Wrong answer — click to see why▾
Why this is wrong here
The symptoms point to CPU overheating (95°C under load) causing thermal shutdown, not power delivery issues. A failing PSU typically causes random shutdowns or failure to boot, not consistent thermal behavior.
★ When this WOULD be the correct answer
A desktop shuts down randomly under load, but CPU temperatures are normal (e.g., 60°C under load). The PSU fan is noisy or stops spinning, and the system fails to power on after shutdown. This indicates a failing PSU.
Why candidates choose this
Candidates may associate unexpected shutdowns with power supply failure, overlooking the clear thermal evidence from sensor readings.
✗The motherboard VRM is overheating.Wrong answer — click to see why▾
Why this is wrong here
The motherboard VRM overheating would typically cause throttling or shutdown under load, but the symptom of CPU temperature rising to 95°C and then shutting down points directly to CPU overheating, not VRM. The VRM issue would not cause the CPU temperature sensor to read 95°C.
★ When this WOULD be the correct answer
A question where a computer shuts down under load, but CPU temperature is normal (e.g., 60°C), and the VRM area on the motherboard is hot to the touch or has visible damage. The correct answer would be 'Motherboard VRM is overheating' due to inadequate cooling or failed VRM components.
Why candidates choose this
Candidates may confuse VRM overheating with CPU overheating because both can cause shutdowns under load, and they might not understand that VRM issues do not directly cause high CPU temperature readings.
Analysis generated from the official 220-1101blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1101 exam.