Fujitsu Mini-Split Blinks 3 times, at intervals of 21 seconds: Air filter cleaning reminder (LPAS series)
Updated October 2026 · Sourced from Fujitsu documentation
✅ Usually fine to keep running
The manual says to clean the air filter when the indicator lamp shows this blinking pattern. It is a reminder, not a fault.
Is it safe to keep running? Usually yes. No service needed unless the lamp keeps blinking after cleaning and resetting.
Blinks 3 times, at intervals of 21 seconds at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| Blinks 3 times, at intervals of 21 seconds Indicator lamp blinks 3 times every 21 seconds | Air filter cleaning reminder (LPAS series) | ASUH18-24LPAS wall-mounted series (with WLAN adapter option) |
Check this first
Only steps a homeowner can do safely. Do not open electrical panels or the burner area.
- Clean the air filter as the manual describes.
- After cleaning, push the filter reset button on the indoor unit for 2 seconds or less.
🛑 Stop and call a licensed pro if
- No service needed unless the lamp keeps blinking after cleaning and resetting.
- Any code pointing to refrigerant, the compressor, high pressure or the outdoor unit board. Refrigerant work legally needs a certified technician.
- Burning smell, sparks, or a breaker that trips again after a reset.
- Water leaking from the indoor unit that does not stop after the drain is clear.
Safe first steps for any Fujitsu code
- Write down the exact code and how it shows (remote display or number of lamp blinks). Similar codes mean different things on different series.
- Turn the system off at the remote, switch off the breaker or disconnect for the unit, wait a few minutes, then turn it back on.
- Clean or replace the indoor unit air filters, and make sure nothing blocks the indoor or outdoor unit.
- Check that the condensate drain line is not blocked or kinked where you can see it.
- Replace the remote controller batteries if the display is dim or the unit does not respond.
Source: Fujitsu General Operation Manual ASUH18-24LPAS, p.8. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.
Shaun Cain · Certified HVAC & Refrigeration Technician · Ask an HVAC technician
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