Why Is My Cooler Not Mounted?

Quick Answer

If your motherboard or monitoring software shows 'CPU cooler not mounted', it usually means the cooler's fan header isn't plugged into the CPU_FAN connector, the fan tach signal isn't reaching the board, or BIOS thinks the cooler RPM is zero. It's almost always a cable or BIOS setting, not a hardware fault.

Check the CPU_FAN Header First

Motherboards detect cooler presence by reading the CPU_FAN tach signal. If your AIO pump is plugged into AIO_PUMP and the radiator fans are on CHA_FAN, the board sees zero RPM on CPU_FAN and throws the warning. Move at least one radiator fan to CPU_FAN, or swap the pump cable to CPU_FAN if the manual recommends it. For air coolers, plug the included fan directly into CPU_FAN, not an extension splitter.

Disable the BIOS Fan Speed Warning

Most ASUS, Gigabyte, MSI, and ASRock boards ship with a CPU Fan Speed Low Limit set to 600 RPM. Some quiet AIOs idle below that. In BIOS, navigate to Hardware Monitor or Q-Fan Control, find CPU Fan Speed Low Limit, and lower it to 200 RPM or set Ignore. The warning disappears immediately on next boot.

Faulty Cable or Failed Pump

If you've checked headers and BIOS and the warning persists, swap the cooler's PWM cable end-for-end on the header. A bent pin, broken tach wire, or dead pump motor will all trigger the same message. AIOs from 2020 onward sometimes fail at the pump, so check whether the cold plate gets warm after a few minutes of CPU load. No warmth means a dead pump.

SA Replacement and Warranty Options

Evetech stocks ARCTIC, Cooler Master, NZXT, Corsair, and DeepCool air and AIO coolers from R399 to R3,499, with same-day Gauteng and Cape Town delivery. All units carry full SA warranty handled locally, no overseas RMA mess. If your current cooler is under two years old, raise an Evetech warranty claim before buying a replacement.

Frequently Asked Questions

Can I just ignore the cooler not mounted warning?

Only if you've confirmed the CPU temps stay safe under load. The warning exists to prevent a thermal-runaway boot when no cooler is fitted. Verify temps with HWiNFO64 or Ryzen Master before silencing it permanently.

Why does my AIO show as not mounted only after BIOS update?

BIOS updates often reset fan curves and re-enable the low-limit warning. Re-enter BIOS, set CPU_FAN low limit to Ignore, save, and reboot. Your custom fan profile may also need to be reapplied through the manufacturer's software.

Will a CPU run damaged if booted without a cooler mounted?

Modern Ryzen and Intel CPUs throttle hard within seconds and shut down before damage. Older chips were less forgiving. Either way, never run benchmarks or load tests until the cooler is fully seated and detected.