Symptoms
- No pump hum or vibration felt on the water block or pump housing
- CPU temperatures spike very quickly under any load
- Radiator fans run, but there's no sign the coolant is circulating
- AIO cooler's software (if any) reports a pump speed of 0
Likely causes
- CommonPump's power cable not connected to the motherboard or a fan hubAIO pumps typically need their own dedicated cable connection separate from the fans.
- PossiblePump cable connected to a header that's set to ramp down or off at low loadSome headers behave like fan headers and can be miscontrolled by BIOS settings.
- PossiblePump motor has failedAIO pumps can fail after years of use, ending the unit's cooling ability.
- Less commonAir lock or manufacturing defect in a new AIO coolerOccasionally a new unit can have an issue preventing proper circulation.
What to do
- Power down immediately if you suspect the pump isn't running, since CPU temperatures can rise very fast without it.
- Check that the pump's cable (often separate from the fan cables) is connected to a header, commonly labeled CPU_FAN or a dedicated pump header per the cooler's manual.
- Check BIOS to make sure that header isn't set to a fan curve that could reduce speed to zero.
- Feel gently for vibration or listen for a faint hum from the pump housing to confirm whether it's truly silent.
- If the pump doesn't respond on a confirmed working header, it has likely failed.
- Replace the AIO cooler if the pump is confirmed dead, since these units generally aren't user-serviceable.
Tools and parts
Replacement AIO liquid coolerSearch: “AIO CPU liquid cooler compatible with your socket”
When to call a pro
A failed AIO pump means replacing the whole cooling unit; a repair shop can confirm the diagnosis if you're unsure whether it's truly not running.
Safety
Use caution
Shut the system down right away if you suspect the pump has stopped, since a CPU can overheat within seconds to minutes without active liquid circulation.