Daikin Aircon A3 Error Code
Daikin A3 is a drain protection fault. The unit is detecting water where it should not be, usually from a blocked drain, float switch, or drain pump issue.
Daikin A3: What It Means
Daikin A3 is a drain protection fault. The unit is detecting a drain-level problem and is shutting down to prevent overflow.
Blocked drain pipe, trap, or concealed drain route.
Float switch triggered because the drain pan is holding too much water.
Failed drain pump or poor drain slope on cassette and concealed units.
What To Do Now
Use these steps before running the unit again or approving drain or pump work.
Stop using the unit if A3 returns
Also stop if water is leaking or the drain pan is filling. A3 is an overflow-risk code.
Reset A3 once if dry
You can switch the system off once and check for obvious water overflow, but do not keep running it if A3 returns.
Send these to us
A3 display, where water appears, wall-mounted/cassette/concealed unit type, and photos of the drip area
What To Check Before Repair
Use this split to confirm overflow risk before approving pump or drain work.
| You Can Check | Technician Should Confirm |
|---|---|
| Switch the unit off if water is leaking or the drain pan is filling. | Clear and flow-test the drain path, including concealed sections where accessible. |
| Take photos of where the water appears: front casing, trunking, ceiling, or drain outlet. | Test the drain pump, float switch, pan level, and pump power supply. |
| Do not keep running the unit to see whether the water clears by itself. | Check installation slope and trap condition if A3 returns after clearing. |
What Changes The Next Step
These clues separate a simple blocked drain from pump, slope, or concealed-route issues.
| What You See | What It Points To |
|---|---|
| Wall unit leaks from the front casing. | A blocked drain pipe, drain pan buildup, or outlet restriction is more likely. |
| Cassette or concealed unit shows A3. | Drain pump, float switch, ceiling route, or trap condition needs priority checking. |
| A3 returns after the drain is cleared. | Pump, float, slope, or concealed-route diagnosis is needed before another clearing quote. |
Drain Repair Or Pump Decision
A3 normally stays in repair scope: clear the drain, test the pump, confirm the float switch, and check slope. Replacement only enters the conversation when the unit is old and access or concealed drainage work makes repair poor value.
A blocked drain is a service-level repair if water flows properly after clearing.
Pump or float-switch faults need part testing before replacement is quoted.
Concealed drain or slope issues can become labour-heavy because access decides the repair path.
Read Next
Use these if the quote mentions drain clearing, float switch, drain pump, or concealed drainage work.
Real Diagnostic Cases
How we approached similar faults on actual jobs.
Need A Clear Next Step?
Send where the water appears, the unit type, the A3 display, and what happened after reset. We can help separate drain clearing from pump or concealed-route work.