Why do my PC fans tick when I boot up?

Start by checking for a cable brushing against a fan blade. Shut the PC down, unplug it, and look around each fan with a light. A thin fan cable can be easy to miss.

Also check whether a blade or the fan frame is rubbing against the case. A slightly bent panel or an overtightened mount can put things out of alignment. Move any loose cable clear and secure it so it can't fall back into the blades.

If nothing is touching the blades, a worn bearing is another possibility. Look for a fan that wobbles or spins unevenly, then replace that fan rather than assuming the whole set is bad.

Try to locate the sound by listening near each fan while the PC runs, keeping fingers and loose clothing away from the blades. You may need to open the side panel to hear it clearly.

The fact that it happens on boot doesn't rule out a fan. The noise can change with fan speed, so it might become less noticeable once the fans speed up or settle down.

Keep an eye on temperatures and whether all the fans are spinning. If a fan stops, slows noticeably, or temperatures rise, shut the PC down and address it before continuing to use it.

Dust and vibration can make fans noisy too, though ticking could have several causes. With the PC off and unplugged, clear accumulated dust and check that the fan and surrounding panels are secure. If the sound remains, narrow down which fan is responsible before buying a replacement.