Why Does My Aircon Fan Keep Running After Turning Off?
A short fan run after shutdown is usually a built-in drying cycle to prevent mould on the coil. But if the fan keeps running far longer than usual, or stops unpredictably, the control path is likely at fault.
By Team Snowflake | Updated 20 Sept 2026
Why does my aircon fan keep running after I turn it off?
- A short post-off fan run is normal drying-cycle behaviour on many units.
- A sticky fan relay can hold the fan running well after the stop command.
- Unstable mains power can leave the off command partially executed.
1. Normal post-off drying cycle
You switch the unit off and the fan keeps blowing for a short stretch before stopping by itself. Many units use this post-off run to dry moisture from the evaporator coil. It reduces mold growth while the unit is idle. A short, consistent delay is usually design behavior, not a fault.
How to tell
A normal drying cycle stops on its own within the duration described for that model. In contrast to a relay fault, the fan does not keep running indefinitely. Check the model instructions rather than assuming every aircon has the same post-off behaviour.
- Fan stops on its own after a short period.
- No unusual smell or noise during the run-on.
- Next startup is normal.
How we confirm it
We confirm the run-on duration matches the model's built-in drying cycle before treating the pattern as a repair case.
Do not approve a board replacement based on a short post-off run. Check the unit's settings for an auto-dry or self-clean mode first. The behaviour is usually documented in the manual.
2. Sticky fan relay or stop-command path fault
You send the off command and the fan keeps spinning far past the normal drying delay, sometimes needing the isolator to stop it. The indoor PCB fan relay should open on off command. If the contact sticks or welds shut, the fan circuit stays closed.
How to tell
Continued running beyond the model’s stated post-off cycle needs checking. Unlike a normal drying delay, it may not stop on its own or may restart unexpectedly. Whereas burning smells or breaker trips call for a safety stop, run-on alone does not identify which control component has failed.
- Fan run-on feels much longer than usual.
- Remote off command response is inconsistent.
- Pattern repeats across different attempts.
How we confirm it
We test relay switching response and board output signals to confirm whether the relay is stuck or the board is not sending the stop command.
Do not replace the fan motor before relay switching response is tested. The relay is the cheaper first check, and a sticky contact produces the same surface symptom as a failing motor.
Related cases
3. Unstable mains disrupting stop sequence
The fan keeps running after off, and there is also a burning smell, breaker trip, or irregular fan speed. Unstable mains power or PCB logic supply can interrupt the off-command sequence. The compressor may stop while the fan relay misses its stop pulse.
How to tell
Physical symptoms alongside the fan run-on are the distinguishing markers: a burning odour near the indoor unit, a breaker trip with operational changes, or the fan running at irregular speeds. In contrast to a normal drying delay, the run is not predictable. A pure relay fault would not involve electrical stress on the motor circuit, but this issue does.
- Burning or electrical odour appears.
- Breaker trip appears with operation changes.
- Fan behaviour is erratic with power events.
How we confirm it
Stop repeated on-off testing. We check voltage stability at the board and inspect relay contacts for arcing or heat damage.
Stop using the unit if you smell burning or hear unusual motor sounds. Turn the isolator off and do not attempt further on-off cycling until the electrical fault is assessed.
Describe your situation
Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.