Daikin fault code A5
High-pressure control / freeze-up protection.
What A5 actually means
High pressure control or freeze-up protection has activated. In cooling it usually means the outdoor unit cannot get rid of heat; in heating it usually means the indoor coil has iced up.
What causes it
- Dirty indoor filters, which is the first thing to check every time
- Outdoor coil blocked with dust, grass clippings or lint
- Something restricting airflow to the outdoor unit
- Outdoor fan failing
- Refrigerant charge wrong
Most likely first. That order is from what we actually find on site, not from the manual.
Safe to check yourself
No tools, no covers off, nothing to do with gas, refrigerant or wiring.
- Take the indoor filters out and wash them
- Hose the outdoor coil down gently with the unit off
- Clear at least 30 cm around the outdoor unit
- Leave it off for an hour if the indoor coil has iced, then restart
What we check on site
So you know what you’re paying for.
- Chemical coil clean if a hose has not done it
- Refrigerant pressures against the spec for the ambient
- Outdoor fan motor and capacitor
- Airflow measurement across the indoor coil
Can you keep using it?
It is a protection code rather than a damage code, so it is not urgent in the way U0 is. But it will keep tripping until the airflow problem is fixed, and running a system that keeps hitting high pressure is hard on the compressor.
What the fix usually involves
More often than not this is a proper coil clean, indoor and outdoor, and nothing else. That is a service, not a repair.
Is it worth fixing?
That depends almost entirely on how old the unit is. Past about ten years on hot water and gas heating, and twelve on aircon, a significant repair usually costs more per remaining year than a replacement does — and it’s the same point at which the VEU rebate is worth the most, because old inefficient appliances are exactly what the scheme pays to remove. If yours is young and the fault is a component, we’ll fix it and say so.
Repair or replace? The 10-year rule, and what the rebate is worth →