Daikin Error Codes Explained: 2026 Lookup Tool & Engineer's Guide

If your Daikin air conditioner has flashed an error code at you, you're not alone. Daikin units talk to engineers through a small alphanumeric code, and that code tells you exactly what tripped, where, and how serious it is. The trick is knowing whether you can clear it yourself in five minutes or whether running the system any longer will make the repair bill three times bigger.

This guide is built from Daikin's own service literature plus 20 years of London callouts at Be Cool Refrigeration. We've put a live lookup tool below so you can paste your code in and get a plain-English explanation, plus the next steps. After the tool you'll find a deeper walk-through of how the codes are organised, the most common faults we see in domestic and commercial systems, and when you genuinely need an F-Gas certified engineer rather than a homeowner-level reset.

How Daikin Error Codes Work

Every Daikin error is a letter followed by a number, sometimes a letter. The letter is the system, the digit is the specific fault. So U4 means a U-series (communications) fault, sub-code 4 (indoor-to-outdoor link). Once you understand the letter system, even an unfamiliar code becomes readable at a glance.

Series	What it covers	Severity
A	Indoor unit faults: PCB, drain, fan motor, expansion valve	Mixed
C	Indoor temperature and humidity sensors (thermistors)	Usually low
E	Outdoor unit faults: PCB, fan, compressor, pressure switches	Often critical
F	Discharge or coil temperature trips	Critical
H	High-side problems: pressure switches, current sensors, motor signals	Often critical
J	Outdoor sensor faults: discharge pipe, suction pipe, ambient	Medium
L	Inverter / electrical box: overcurrent, heatsink temperature	Critical
P	Other PCB-side issues including capacity setting mismatches	Medium
U	System and communication errors between units and controllers	Mixed

Reading the Code on Your Remote

How you see the code depends on which controller you have.

Wireless ARC remote (typical split system)

1. Press and hold the CANCEL button for around five seconds.
2. The display will show 00 and beep continuously.
3. Press CANCEL again to step through codes — the unit will give a long beep when it hits the active error code.
4. Note the code, then press CANCEL once more to exit.

BRC1E / BRC1H wired controllers (commercial units)

1. The error code shows automatically on the bottom row of the screen.
2. Press Menu / OK to drill into the fault history.
3. The most recent ten faults are stored, with timestamps if the controller has a real-time clock fitted.

Madoka and newer touch controllers

Tap the warning triangle to bring up the active code. Long-press it to see the history.

Daikin Error Code Lookup Tool

Type your code below. The tool covers the codes we see most often in the field, with a clear explanation and a short list of what to check next. Severity is colour-coded so you know whether to keep using the unit or shut it down.

The Five Most Common Daikin Errors We See in London

About 70 per cent of our Daikin call-outs are one of these five codes. If yours is on the list, the section below will tell you whether to attempt a reset or book us in.

U4 — indoor and outdoor cannot communicate

This is by far the most common one. The two units share a small data signal over the interconnect cable. When that signal drops, neither unit knows what the other is doing and the system shuts down. Causes we see weekly:

• A loose terminal screw on the outdoor unit, often after a windy week.
• The polarity is wrong on terminals 1, 2 and 3 — Daikin is strict about this and the system will not run if they're swapped.
• A nail or staple has gone through the cable inside a wall (yes, really).
• The outdoor unit has lost mains power because the isolator was left off after a service.

If you can safely access the isolator, switch it off, wait two minutes, switch it back on, and watch for U4 to clear. If it returns within an hour, stop and book an engineer. If our London air conditioning installation team installed the unit, we'll usually have the wiring records on file.

E3 — high-pressure switch tripped

This means the discharge pressure inside the system has climbed past Daikin's safety limit. Almost every E3 we attend is one of three things:

• The outdoor coil is matted with leaves, fluff or pollen and the unit can't reject heat.
• Something has been built or planted within the airflow zone of the outdoor unit (a fence, a shed, a row of conifers).
• The system has been overcharged by a previous engineer.

It is not safe to keep cycling the unit through E3. Discharge pressure spikes quickly damage the compressor, and a compressor is the single most expensive component in the system. Clean the outdoor coil if you can do so safely, and clear at least 30 cm of breathing room on every side. If E3 returns within a week, we need to verify subcooling and superheat before running the unit again.

A3 — indoor drain water level abnormal

Cooling produces condensate. Around 5 to 20 litres a day from a typical wall split working hard in summer. That water has to leave the unit, and the drain path is the part of the install most likely to fail over time.

A3 specifically means the float switch in the drain pan has detected a high water level. Two main causes:

• The condensate pump has failed, so water sits in the pan instead of being pumped out.
• The drain hose is partly blocked by biological slime or has frozen up over winter.

Switch the unit off in cooling mode the moment A3 appears or you risk water dripping through the ceiling. Heating mode is fine because it doesn't produce condensate. Closely related: read our piece on why an AC leaks water for the full diagnosis tree.

U0 — insufficient gas (refrigerant low)

U0 is Daikin's polite way of saying the system has lost charge. It does not lose charge through normal use. If U0 has appeared, you have a leak. Top-up without leak repair is a breach of the UK F-Gas Regulations 2015 and any engineer who pumps gas into a leaking system without finding the leak is acting unlawfully.

What we'll do: pressure test, leak detect with electronic sniffer, repair, evacuate, weigh in fresh charge to the spec on the unit's data plate. We strongly recommend reading our refrigerant types guide if you want context on what charge your unit uses.

A6 — indoor fan motor fault

Modern Daikin indoor units use brushless DC fan motors that report their speed back to the PCB. When the speed feedback drops out, the unit assumes the motor has failed and stops the system. Rarely a wiring issue, almost always a worn motor.

You can confirm if you turn the unit on and listen — if the fan never spools up, A6 is real. If the fan runs and A6 still appears, it's a feedback wire. Either way it's an engineer fix because DC fan motors carry residual voltage on their terminals and aren't safe for DIY.

Resetting a Daikin After a Fault

The unit has its own reset routine that's safer than just pulling the plug.

1. Switch the unit off at the wireless or wired controller.
2. Switch off at the wall isolator (the small grey switch with a red dot — it lives near the outdoor unit and sometimes near the indoor unit too).
3. Wait five full minutes. The capacitors inside the inverter PCB take this long to discharge.
4. Switch the isolator back on.
5. Wait two more minutes for the system to handshake.
6. Run the unit. If the same code returns within an hour, you have a real fault, not a glitch.

Don't try a reset more than twice. Repeated resets through a real fault can stack damage on top of damage, especially with anything compressor-related (E5, E6, L5, L8).

When to DIY and When to Call an Engineer

Code or symptom	Try yourself first	Call an engineer
Filter dirty, weak airflow	Yes — clean filters, see our filter guide	Only if cleaning doesn't fix it
U4 (one-off)	Yes — power-cycle once	If it returns within an hour
U5 (remote)	Yes — replace remote batteries, re-pair	If wired controller
A3 (drain)	Switch off cooling immediately	Yes, every time
E3 (high pressure)	Clean outdoor coil	Always, after first cleaning
U0 / leak	No	Always — F-Gas obligation
Anything compressor-related (E5, E6, H6, L5)	No	Always — stop running unit
Anything PCB-related (A1, E1, H0)	No	Always

Preventing Error Codes in the First Place

Most of the codes above are avoidable with a half-day of preventative maintenance once a year. The cheapest five things you can do to stay out of fault states:

• Clean indoor filters every four to six weeks during heavy use.
• Hose down the outdoor coil every spring before the cooling season.
• Clear at least 30 cm of breathing room on every side of the outdoor unit.
• Run the heating mode for ten minutes once a month over winter to keep the compressor seals lubricated.
• Get a proper service every twelve months. Read our pre-season checklist for what we run through.

If you run a commercial system with an effective rated output of 12kW or more, you also have a legal obligation. Read our TM44 inspections guide for what's required and the £300 fines if you skip it. The TM44 inspection itself often catches issues that would otherwise produce an error code six months later.

Frequently Asked Questions

Why does my Daikin keep showing the same error code after a reset?

Because the underlying fault hasn't been fixed. A reset clears the latched fault state but does nothing to the cause. If the same code returns within an hour, treat it as confirmed and book an engineer.

Can I clear a Daikin error code by removing the batteries from the remote?

No. The error is stored in the indoor unit's PCB, not the remote. The only way to clear it is at the unit itself, either by power-cycling at the isolator or by using the engineer's reset routine on a wired controller.

Is it safe to keep using my Daikin with an active error code?

It depends on the code. Sensor faults (the C and J series) are usually safe to run on for a few days while you wait for an engineer. Pressure or compressor codes (E3, E4, E5, E6, U0, L-series) are not — keep using the unit and you can turn a £300 sensor swap into a £2,000 compressor replacement.

How much does it cost to repair a Daikin error code in 2026?

Sensor swaps and drain unblocks: around £180 to £350 including parts and labour. PCB replacements: £450 to £900. Compressor replacements: £1,400 upwards on a small split, more on multi-systems. A leak repair plus regas is typically £350 to £600. Read our full AC repair and replacement cost guide for the breakdown.

Are Daikin error codes the same on all models?

The major codes (the U, A, C, E, H families) are consistent across the entire Daikin range, from a domestic FTXM split to a commercial VRV system. The exact sub-codes within a series can vary slightly, especially on the latest VRV 5 hardware. The lookup tool above covers the codes that match across the consumer and light commercial ranges, which is over 90 per cent of what we see.

Does my Daikin warranty cover error code repairs?

Daikin's standard warranty covers manufacturer faults on parts for three years on residential and five years on commercial, provided the unit has been serviced annually by an F-Gas certified engineer. Wear-and-tear (filters, blocked drains, refrigerant top-ups due to leaks) is not covered. Keep your service records — without them, Daikin will reject claims.

Talk to a Real Engineer

If your code isn't on the list above, or it is but you'd rather have a professional look at it, we cover all of London for Daikin repairs. Most jobs are diagnosed on the first visit, and we carry common spares (PCBs, sensors, capacitors, fan motors) on the van so we can fix the same day where possible. Book a callout via the form on the homepage or call 0203 488 1889. You can also browse our comparison of London AC companies if you want to see how we stack up before deciding.