CPU Overheating: Thermal Paste Not Applied
A technician upgrades the CPU in a desktop computer and installs a new aftermarket cooler. After reassembly, the computer powers on but shuts down after about one minute. The technician enters the BIOS and sees the CPU temperature is 95°C and rising. The case fans are spinning normally. Which of the following is the MOST likely cause of the issue?
Quick Answer
The answer is that the thermal paste was not applied between the CPU and the cooler. Without thermal paste, microscopic air gaps form between the CPU die and the cooler’s base plate, which act as insulators and prevent efficient heat transfer. This causes the CPU to spike to 95°C and rising immediately after power-on, triggering a thermal shutdown within a minute—even though the case fans spin normally. On the CompTIA A+ Core 1 220-1101 exam, this scenario tests your understanding of proper CPU cooler installation and thermal management; a common trap is to suspect a faulty fan or power supply, but the rapid temperature rise points directly to poor contact. Remember the memory tip: “No paste, no haste—heat will waste.”
⚠ Common exam trap
Watch out — candidates often assume a fan failure (Option D) is the cause because overheating is often associated with a non-spinning fan, but the question explicitly states the case fans are spinning, and the rapid temperature rise at idle points to a thermal interface problem, not airflow.
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 was not applied between the CPU and the cooler
The CPU temperature reaching 95°C and rising immediately after power-on indicates a critical thermal issue. Since the case fans are spinning normally and the cooler fan is not mentioned as faulty, the most likely cause is that thermal paste was not applied between the CPU and the new aftermarket cooler. Without thermal paste, microscopic air gaps prevent efficient heat transfer from the CPU die to the cooler's base plate, causing rapid overheating and thermal shutdown.
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 is not compatible with the motherboard
Why it's wrong here
An incompatible CPU typically prevents POST or produces no boot at all, whereas this system boots and reports a live 95°C reading, so the socket is functioning. It is tempting because the fault appeared immediately after a CPU swap, and would be correct if the board rejected the chip outright with a beep code or blank display.
- ✗
The power supply unit is insufficient for the new CPU
Why it's wrong here
An undersized PSU causes abrupt power loss under load without the BIOS reporting an elevated CPU temperature; 95°C rising points to heat transfer, not wattage. It is tempting because a new CPU draws more power, and would be correct if shutdowns occurred under heavy load with normal thermals.
- ✓
The thermal paste was not applied between the CPU and the cooler
Why this is correct
Without thermal paste, the microscopic gaps between the CPU heat spreader and cooler base fill with air, which conducts heat poorly. The CPU therefore overheats rapidly despite the cooler and case fans running, triggering the thermal shutdown after roughly a minute, matching the 95°C BIOS reading.
- ✗
The CPU cooler fan is not spinning
Why it's wrong here
The question states case fans spin normally, but a non-spinning cooler fan could cause overheating. However, the scenario mentions the cooler is aftermarket and the technician would likely notice if the fan wasn't spinning. The rapid temperature rise is more characteristic of missing thermal paste.
Go deeper
Related to this question
About these practice questions
One of 896 original 220-1101 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
2 more ways 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 assembling a new desktop computer. After installing the CPU, heat sink, RAM, and power supply, the system powers on for a few seconds and then shuts down. The CPU fan spins during that time. The technician has verified that the power supply connections are secure. Which of the following should the technician check FIRST?
medium- A.The RAM module's compatibility with the motherboard
- B.The CPU power connector is fully seated
- ✓ C.The thermal paste application between the CPU and heat sink
- D.The front panel power switch connection
Why C: The system powers on for a few seconds and then shuts down, which is a classic symptom of thermal overload protection (Tjmax) being triggered. Since the CPU fan spins, power delivery is present, but without proper thermal paste, the CPU rapidly exceeds its critical temperature threshold, causing an immediate shutdown to prevent damage.
Variation 2. A technician is assembling a new desktop computer. After installing the CPU, thermal paste, and heatsink, the technician connects all power cables and turns on the system. The fans spin, but the system shuts down after about 10 seconds. Which of the following is the MOST likely cause?
easy- A.The CPU is not compatible with the motherboard.
- ✓ B.The heatsink fan is not connected to the CPU fan header.
- C.The power supply is insufficient wattage.
- D.The RAM is not seated properly.
Why B: The correct answer is B: the heatsink fan is not connected to the CPU fan header. Many motherboards perform a POST check that detects no tachometer/RPM signal on the CPU_FAN header and will halt the boot or power off within seconds to prevent the CPU from overheating, which matches the symptom of fans spinning briefly then shutting down after about 10 seconds. An incompatible CPU (A) typically prevents the system from starting at all or produces a beep code rather than a delayed shutdown, and it would not be affected by the fan header. Insufficient PSU wattage (C) usually causes shutdowns under load or instability rather than a consistent 10-second cutoff at idle, and improperly seated RAM (D) normally results in no POST, beep codes, or a blank screen rather than a timed power-off.
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.