Blinking Temperature LEDs — What They MeanUpdated 2 months ago

If all 5 green temperature LEDs on your aF4 are flashing simultaneously, the unit has detected a fault and is alerting you. This guide will help you identify exactly which fault you have based on when the LEDs started flashing.

How to diagnose your fault

The timing of when the LEDs begin flashing tells you everything. Check which scenario matches your situation:

Scenario 1 — LEDs flash immediately on power-on

Cause: Fan failure

If the LEDs begin flashing within seconds of powering the unit on, the cooling fan has failed or is not spinning correctly. The unit detects no airflow and triggers the fault immediately as a protective response.

What to do: See our Fan & Cooling System Cleaning Guide to inspect the fan. If the fan is obstructed or seized, cleaning may resolve it. If the fan is not spinning at all after cleaning, this is a hardware failure — submit a support ticket for a warranty assessment.

Scenario 2 — LEDs flash within the first 3 hours

Cause: Failed temperature probe

If the LEDs begin flashing shortly after startup — typically within the first 3 hours of operation — this indicates a failed or faulty temperature probe. The probe is reading an incorrect value and triggering the fault prematurely, before the unit has had a chance to reach a genuinely unsafe temperature.

What to do:This is a hardware issue that cannot be resolved by the user. See the Over-Temperature Fault: Remedies & Prevention Guide for the DIY sensor repositioning fix, or submit a support ticket for a warranty assessment.

Scenario 3 — LEDs flash after 3 or more hours of operation

Cause: Over-temperature fault

If the LEDs begin flashing after 3 or more hours of normal operation, the unit's internal temperature has genuinely risen above a safe threshold. This is either caused by environmental factors — such as restricted airflow — or by a faulty over-temperature sensor reading incorrectly over time.

What to do:See our Over-Temperature Fault: Remedies & Prevention Guide for a full walkthrough covering airflow fixes, the DIY sensor repositioning fix, and warranty options.

How your unit responds to the fault

What happens when the LEDs flash depends on your unit's serial number, which determines the firmware version installed.

Serial numbers beginning with 100XXX: Your aF4 enters standby mode automatically and will beep continuously. The cooling system continues to attempt to run, and feeding operations pause. The unit remains powered on. Once the fault is resolved and cleared, it will resume normal operation.

Serial numbers beginning with 20XXX or 60XXX: Your aF4 shuts down completely. The flashing LEDs remain displayed. The unit will not restart on its own — you will need to resolve the cause and manually power it back on after addressing the fault.

Where is my serial number? It is printed on the sticker on the underside of your aF4.

Does the error clear on its own?

No. The fault will not clear automatically even after the unit cools down or is left to sit. You must manually power the unit off and back on to clear the error after the underlying cause has been addressed.

Summary

Not sure which scenario applies to you? Submit a support ticket and our team will help diagnose it.