CPU Overheating to 100°C — Missing Thermal Paste or Protective Film
A technician replaces the CPU and cooler in a desktop computer. After reassembly, the computer boots but shuts down automatically after about two minutes. The technician enters the BIOS and sees the CPU temperature rapidly climbing to 100°C. The CPU cooler fan is spinning at high speed, and the heatsink is firmly attached. Which of the following should the technician check NEXT?
Quick Answer
A CPU temperature that rockets up to 100°C within about two minutes, despite the cooler's fan spinning at high speed and the heatsink being firmly attached, tells you that heat is being generated normally by the CPU but is not being transferred out of it effectively, which points to the interface between the CPU and the cooler rather than the fan or the mounting itself. Thermal paste exists specifically to fill the microscopic gaps between the CPU's surface and the cooler's base, since even surfaces that look flat have imperfections that would otherwise trap insulating air pockets and drastically reduce heat transfer. If the paste was applied unevenly, insufficiently, or was skipped entirely, or if the thin plastic protective film that ships on some cooler bases was never removed, the cooler's base is effectively insulated from the CPU despite being clamped firmly in place, which explains why a properly spinning fan on a properly attached heatsink still fails to prevent overheating. Because the fan and mounting have already been confirmed to work correctly, checking the thermal interface itself is the logical next step before assuming the cooler or CPU is defective. Whenever a freshly reassembled system overheats rapidly despite a spinning fan and a firmly attached heatsink, especially right after a CPU or cooler swap, check the thermal paste and any protective film before suspecting hardware failure.
⚠ Common exam trap
The trap here is that candidates may focus on the fan spinning at high speed and assume the cooler is working correctly, overlooking the critical missing link of thermal interface material or a protective film that prevents heat transfer.
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 application or protective film on the cooler.
The rapid temperature climb to 100°C with the fan spinning at high speed and the heatsink firmly attached indicates that heat is not being transferred from the CPU to the heatsink. The most likely cause is either missing thermal paste or a protective film left on the cooler's base, which acts as an insulator. Checking and reapplying thermal paste or removing the film is the correct next step.
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 CPU voltage settings in the BIOS.
Why it's wrong here
While incorrect voltage can cause heat, it usually takes longer to reach critical temperatures and is not the first suspect when the cooler is newly installed. The immediate rise to 100°C indicates a thermal transfer problem.
When this WOULD be correct
A technician replaces a CPU and the system is unstable or overheating. After verifying proper cooler installation and thermal paste, the technician should check CPU voltage settings if the temperature is high but not rapidly climbing, or if the system crashes under load with adequate cooling.
- ✗
Whether the CPU is compatible with the motherboard.
Why it's wrong here
An incompatible CPU would prevent POST entirely or throttle, not produce a rapid 100°C rise with the heatsink firmly mounted. It is tempting because the CPU was just replaced, but it is correct when the system fails to boot at all.
When this WOULD be correct
A technician installs a new CPU but the computer fails to POST or shows no display. Checking compatibility with the motherboard's socket and chipset would be the correct next step.
- ✓
The thermal paste application or protective film on the cooler.
Why this is correct
Rapidly rising temperature with a spinning fan and seated heatsink indicates poor heat transfer at the CPU interface. A missing, dried or incorrectly applied thermal paste layer, or an unremoved protective film, prevents conduction, so inspecting it is the next logical step.
- ✗
The power supply wattage.
Why it's wrong here
Insufficient PSU wattage causes random shutdowns under load, not a CPU climbing to 100°C with the fan at full speed. It is tempting because shutdowns suggest power faults, but it is the correct check when temperatures remain normal.
When this WOULD be correct
A technician installs a new high-end CPU and GPU, and the computer randomly shuts down under load. The PSU is an older 400W unit. In this scenario, checking power supply wattage would be correct because the system draws more power than the PSU can provide.
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 application or protective film on the cooler.Correct answer▾
Why this is correct
Rapidly rising temperature with a spinning fan and seated heatsink indicates poor heat transfer at the CPU interface. A missing, dried or incorrectly applied thermal paste layer, or an unremoved protective film, prevents conduction, so inspecting it is the next logical step.
✗The CPU voltage settings in the BIOS.Wrong answer — click to see why▾
Why this is wrong here
The CPU voltage settings are unlikely to cause a rapid temperature climb to 100°C within two minutes, especially with the cooler fan spinning at high speed and the heatsink firmly attached. The symptoms point to poor heat transfer, not voltage issues.
★ When this WOULD be the correct answer
A technician replaces a CPU and the system is unstable or overheating. After verifying proper cooler installation and thermal paste, the technician should check CPU voltage settings if the temperature is high but not rapidly climbing, or if the system crashes under load with adequate cooling.
Why candidates choose this
Candidates may think incorrect voltage can cause overheating, but in this scenario the rapid temperature rise despite proper fan and heatsink attachment indicates a thermal interface problem, not a voltage configuration issue.
✗Whether the CPU is compatible with the motherboard.Wrong answer — click to see why▾
Why this is wrong here
The computer boots and runs for two minutes before overheating, indicating the CPU is recognized and functional. Incompatibility would typically prevent boot or cause immediate failure, not delayed shutdown.
★ When this WOULD be the correct answer
A technician installs a new CPU but the computer fails to POST or shows no display. Checking compatibility with the motherboard's socket and chipset would be the correct next step.
Why candidates choose this
Candidates may confuse symptoms of overheating with compatibility issues, or assume that a new CPU might not be supported by the existing BIOS version.
✗The power supply wattage.Wrong answer — click to see why▾
Why this is wrong here
The power supply wattage is not the cause of immediate overheating after CPU replacement; insufficient wattage would typically cause instability or failure to boot, not rapid temperature rise with a spinning fan.
★ When this WOULD be the correct answer
A technician installs a new high-end CPU and GPU, and the computer randomly shuts down under load. The PSU is an older 400W unit. In this scenario, checking power supply wattage would be correct because the system draws more power than the PSU can provide.
Why candidates choose this
Candidates may think a weak PSU causes overheating due to inadequate power delivery, but overheating here is a thermal issue, not a power issue.
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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Same concept, more angles
1 more way this is tested on 220-1101
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A technician is replacing a CPU on a desktop motherboard. After carefully installing the new CPU and reattaching the heatsink, the technician powers on the system. After a few minutes, the system shuts down due to overheating. The technician verifies that the CPU fan is spinning and the heatsink is firmly attached. Which of the following is the MOST likely cause of the overheating?
easy- A.The CPU is not compatible with the motherboard socket
- ✓ B.No thermal paste was applied between the CPU and heatsink
- C.The CPU fan is connected to the wrong motherboard header
- D.The heatsink is installed upside down
Why B: The most likely cause is that no thermal paste was applied between the CPU and heatsink. Thermal paste fills microscopic air gaps between the CPU's integrated heat spreader (IHS) and the heatsink base, ensuring efficient heat transfer. Without it, air acts as an insulator, causing the CPU to rapidly overheat and trigger thermal shutdown, even if the fan spins and the heatsink is firmly attached.
JA
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.