PC turns on then immediately shuts off
Pressing power produces a brief response, then the PC shuts off before it can boot. Start with external power and recent changes. If it stays on without video, use the no-display guide instead.
Try this first
1 quick checks · ~2 min
Find your situation
See all the clues. Choose the one that matches what you observe.
Flash or brief fan movement, then off
Start with external power and accessories, without repeated starts.
Started after RAM, GPU, CPU or cable changes
Compare the change with the manual before further disassembly.
Reaches the logo or leaves LEDs/beeps
Interpret the signal for the exact model and review cooling where relevant.
Repeatedly powers on and off
Stop failure cycles and request a safe assessment.
Diagnostic signals
- ObservationBefore or after POST
- Reaching the logo establishes more progress than an initial flash, but does not rule out power or cooling.
- ObservationAn LED has no universal meaning
- Record label, color and pattern; use that board’s manual rather than a similar one.
Step-by-step solutions
Record the pattern already observed
Choose a path without forcing another startup.
Without provoking more cycles, note how long it stayed on, whether a logo, LED or beeps appeared and what changed immediately beforehand. Distinguish one shutdown from an automatic loop.
If there is smell, smoke, sparking, liquid or visible damage, do not reconnect it and seek service. If it stays powered without video, use the related no-display guide; if it shuts off, choose the pattern below.
Rule out a safe external condition
With the PC off and unplugged, visually check its cord and external connection. Do not use damaged cables or change voltage selectors. Remove nonessential external accessories such as hubs or USB drives without touching internal parts.
If there are no damage signs and this comparison has not been made, use a known safe outlet and make one attempt with the case closed. If it stays on, shut down normally before restoring accessories one at a time. If power cuts again, stop: the changed result points toward the accessory or path but does not prove which part failed.
Review the change preceding failure
From another device check the board model, supported CPU/RAM lists and BIOS requirements. A CPU needing another BIOS is not fixed by repeated starts; do not update firmware while the PC shuts down.
If RAM changed, review recommended modules and slots; if GPU or power changed, review requirements and CPU/GPU connectors in their manuals. A fitting connector does not guarantee compatibility. Request an assembly review before replacing other parts.
If a safe return to the previous configuration removes failure, investigate the change rather than automatically condemning the board. Internal comparison requires the precautions below and experience; it is not part of the quick check.
Use POST and manufacturer signals
Look up the exact LED or beep pattern in the manual. A DRAM LED directs attention to memory and configuration; it does not establish that every module is damaged. If the signal does not remain visible, use existing observations; do not leave exposed hardware energized to view it.
If it reaches the logo and then shuts down, report recent CPU or cooling work. Thermal protection can shut a system down, but duration alone does not confirm it. Have cooler mounting and ventilation reviewed for the model; do not run stress loads or start without cooling.
Stop a power-cycle loop
Do not keep pressing Power to force startup. Power off and safely disconnect following the manual; do not continue failure cycles to complete this guide. Model-documented memory training differs from recurrent failure, but cannot be assumed merely because RAM is new.
If it cannot stay on after the external comparison or you cannot distinguish the behavior, request assistance. Provide duration, changes and signals. Without stable power, reinstalling Windows or updating BIOS is not the next test.
Advanced checks
Continue if the earlier steps did not help. Read each procedure’s precautions first.
Reserve internal inspection for a specific test
Only with experience, permission and the manual: power off, unplug and follow manufacturer residual-power and static precautions before touching anything. If failure began with RAM, review seating and a compatible configuration; if with cables, review CPU/GPU power using only cables approved for that PSU.
Do not make several changes together. Close the case before a justified test. If the correction does not allow stable power, stop and leave assessment with known-compatible components to a technician. Do not test an opened PSU or bridge its connectors.
Still not working?
A PC unable to remain powered needs hardware assessment. Provide board/PSU models, changes, pattern and the result of the safe comparison made. Do not buy parts based only on fans or lights or prolong failure cycles.
Sources
Documentation behind this guide. Editorial recommendations are identified separately.
- ASUSOfficial[Motherboard] Troubleshooting - No Power/No Boot/No Display
- MSIOfficial[Motherboard] What to do if there is no power after booting up or no display on the monitor
- AMDOfficialHow to Troubleshoot Power Supply Issues
- IntelOfficialOverheating Symptoms and Troubleshooting for Intel Boxed Processors
Source review: . A documentation review, not a physical hardware test.
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