Member Avatar for H2oWorm
H2oWorm 0 Newbie Poster

HELLLLLLLLLLLP!!!!!!!!! When I shut down my computer the fan gets extremely loud. the only way to quiet it down is to unplug it. when I plug it back in it's still loud UNTIL I power on the machine, then it's normal/quiet. Do I need to replace the Power supply??

  • 1 Contributor
  • 0 Replies
  • 134 Views

Dani AI

Generated

Short expert note for : when a fan gets very loud while the PC is shut down but quiets after a normal boot, the most likely causes are (A) the PSU or its fan-control electronics behaving oddly in standby, or (B) a case/CPU fan wired to a power rail that is still energized in soft-off so it spins uncontrolled until the motherboard takes over on boot. Both are common and fixable — start by isolating which fan it is before replacing parts.

Quick, safe troubleshooting (in order):

  1. Observe during shutdown to localize the noise (back grille = PSU fan; front/top = case fan; around CPU cooler = CPU fan). Do not put fingers near moving fans.
  2. If the PSU fan is the culprit: stop using the PSU for long periods and plan a replacement. Do not open the PSU — dangerous capacitors.
  3. If a case/CPU fan: power down, unplug AC, open the case and check how the fan is powered. A Molex adapter to the PSU gives constant 12V; a 3/4-pin on the motherboard allows BIOS control. Move fans to motherboard headers or replace the fan with a quieter model if needed.
  4. Check BIOS/UEFI fan control settings (smart/PWM/DC profiles). Some boards only apply curves after boot, so a fan may run full during standby.
  5. If unsure, swap in a known-good PSU or have a shop bench-test it.

Cautions and final tips: do not attempt PSU repairs at home. If the noisy unit is the PSU and it behaves strangely only when plugged in but off, replacement is the safest option — a failing PSU can cause larger problems. If this is a motherboard/fan-header behavior, using proper headers or a fan controller is the clean fix.

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.