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Desktop PC · Repair Copilot

PC won't POST

A PC that powers on — fans spin, lights come on — but shows nothing on screen has failed to POST. It's almost always a seating or cabling issue: RAM in the wrong slots, a loose EPS/CPU power cable, the monitor plugged into the motherboard instead of the GPU. Show SightLine the inside of the case and it walks you through the checks builders use, in order.

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Steps to fix pc won't post

  1. Confirm both power cables are seated: the 24-pin main AND the separate 4/8-pin EPS/CPU power up top.
  2. Plug the monitor into the GPU's output, not the motherboard's (a discrete GPU disables the onboard port).
  3. Re-seat the RAM in the correct dual-channel slots (usually A2/B2 — the 2nd and 4th from the CPU) until the clips snap.
  4. Look for a motherboard debug LED or listen for beep codes to see what stage it's failing at.
  5. Re-seat the GPU in the top PCIe x16 slot until it clicks.
  6. Clear CMOS (or pull the battery briefly) to reset a bad BIOS setting; update BIOS if the CPU is newer than the board.

Safety first: if a step calls for gas, a main water or sewer line, a service panel or main breaker, or a sealed refrigerant system, stop and call a licensed pro — Repair Copilot will tell you when you're there.