Daikin Error Code A3: Drain Water Level Problem (Meaning, Causes, Fixes)

What the code means

Daikin names A3 "Drain Level Control System Abnormality" (older European manuals call it "Malfunction of Drain Water Level System"). It applies to Daikin indoor units that have a condensate drain pump and float switch, such as ceiling cassettes (FXFQ, FXZQ, FCQ, FFQ), ceiling suspended (FXUQ), ducted (FXDQ, FXSQ, FXMQ, FBQ) and some other ducted and concealed models. Daikin detects the error from the float switch: the water in the drain pan has risen to its upper limit and the float switch has turned OFF, so the unit stops to keep the pan from overflowing. Daikin's quick malfunction code chart lists the supposed causes as drain clogging or an upward slope in the drain piping, a defective drain pump, and a defective float switch or short circuit connector. US service manuals add that a missing 208-230 V power supply, a loose connector and a defective indoor unit PCB can also trigger it. Standard wall-mounted mini splits without a drain pump normally don't use A3.

Likely causes

• A clogged condensate drain line or drain pan, from algae, slime, dust or debris, so water backs up and lifts the float.
• Drain piping installed with an upward slope or a sag, which Daikin specifically lists as a cause.
• A failed or disconnected drain pump that no longer lifts water out of the pan.
• A defective float switch, or a missing or faulty short circuit connector on units that don't use a float switch.
• A loose connector between the float switch or drain pump and the indoor unit control board.
• No 208-230 V power supply reaching the indoor unit, so the drain pump can't run.
• A defective indoor unit control PCB.

Safe DIY checks

1. Turn the system off at the remote and switch off the breaker for the indoor unit before touching anything.
2. Check for signs of water at the indoor unit, such as drips from a ceiling cassette or water around a ducted unit's drain pan. Water there backs up the drain-blockage explanation.
3. Find where the condensate line ends outdoors or at a drain and make sure the outlet isn't blocked, buried, frozen or crushed.
4. If the line has an accessible cleanout, clear it with a wet/dry vacuum from the outlet end, or flush it with a cup of water to confirm it flows freely.
5. Look along any visible drain pipe for sags or uphill sections. Daikin lists an upward slope as a cause, and it usually needs the installer to fix.
6. Restore power and run the unit in cooling. If A3 comes back, stop and call a technician, since the pump, float switch and board aren't owner parts.

Parts that commonly fix it

Always match the part number to your exact model.

Related codes

• U4 Daikin Mini Split U4
• 53 Fujitsu Mini Split 53
• E6 Mitsubishi Mini Split E6
• E9 Mitsubishi Mini Split E9
• 002 AO Smith Electric Water Heater 002

All Daikin codes →

Sources

1. Daikin service manual SiUS342003E (VRV RXYQ-XA series), p.22 "Drain Level Control System Abnormality" A3: float switch OFF detection, supposed causes and troubleshooting flow, via ManualsLib
2. Daikin Industries, Simple Self-Diagnosis by Malfunction Code (A3 Drain Level Control System Abnormality: drain clogging, upward slope, defective drain pump, defective float switch or short circuit connector)
3. Daikin Comfort, Daikin One error codes list (A3 float switch error, safety error: check drain for clog, drain pump, indoor PCB, power)
4. Daikin service manual ESIEN05-04, p.3-33 "Malfunction of Drain Water Level System (A3)": water level at upper limit and float switch OFF; causes