The correct next step is to test the power supply using a PSU tester. When a PC won’t power on and the PSU fan is not spinning, the power supply is the primary suspect because the fan’s failure to spin indicates it is likely not receiving or delivering power, even with a verified connection. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your ability to follow a logical troubleshooting process, starting with the most probable and easily tested component before moving to the motherboard or CPU. A common trap is to immediately replace the power supply without confirming it is faulty, or to waste time reseating RAM or checking the front panel headers first. Remember the memory tip: “No spin, PSU’s the sin” — if the fan doesn’t spin, isolate the PSU with a tester before anything else.
220-1101 Core PC Hardware Troubleshooting Practice Question
This 220-1201 practice question tests your understanding of core pc hardware troubleshooting. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A client brings in a desktop that will not power on. The technician verifies the power cord is connected and the PSU fan does not spin when the power button is pressed. What is the most appropriate next step?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Test the power supply using a PSU tester
When the PSU fan does not spin, the power supply may be dead. The quickest and safest test is to use a power supply tester or perform the paperclip test to see if the PSU turns on. If it does not, replacement is needed. Always eliminate the PSU as the cause before checking other components.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Replace the motherboard
Why it's wrong here
Replacing the motherboard is premature without first testing the PSU.
✓
Test the power supply using a PSU tester
Why this is correct
A PSU tester confirms whether the power supply is delivering correct voltages; if not, the PSU is the problem.
Related concept
Static NAT maps one inside address to one outside address.
✗
Reseat the CPU
Why it's wrong here
A CPU issue would not prevent the PSU fan from spinning; the PSU itself is suspect.
✗
Check the front panel power switch
Why it's wrong here
While possible, a faulty power switch is less common than a dead PSU, and the PSU fan should still spin if the switch is bypassed.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 220-1201 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
Core PC Hardware Troubleshooting — This question tests Core PC Hardware Troubleshooting — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Test the power supply using a PSU tester — When the PSU fan does not spin, the power supply may be dead. The quickest and safest test is to use a power supply tester or perform the paperclip test to see if the PSU turns on. If it does not, replacement is needed. Always eliminate the PSU as the cause before checking other components.
What should I do if I get this 220-1201 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
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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 customer brings in a PC that was working fine until they moved it to a new desk. Now it powers on but immediately shuts off after 2 seconds. The technician notes that the CPU fan does not spin at all. What is the most likely cause?
hard
A.The power supply is failing under load.
✓ B.The CPU fan header is disconnected from the motherboard.
C.The CPU is not seated properly.
D.The case power button is stuck in the pressed position.
Why B: Immediate shutdown after power-on is often a protection mechanism triggered by a missing CPU fan signal. The CPU fan not spinning at all suggests the fan connector is loose or unplugged, which is common after moving a PC.
Variation 2. A customer complains that their computer will not turn on. The power supply fan does not spin, and the motherboard LED is off. The technician tests the power supply with a multimeter and gets 0V on all pins. What should the technician do next?
medium
A.Replace the motherboard.
B.Reseat the 24-pin power connector.
✓ C.Replace the power supply with a known-good unit.
D.Check the wall outlet with a voltage tester.
Why C: A power supply that outputs 0V on all pins is likely dead. The correct next step is to replace it with a known-good unit to confirm the diagnosis, as the PSU is the most probable failed component.
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