Next Phase Heating is an independent HVAC contractor. We are not an authorized dealer for, or affiliated with, any equipment manufacturer. Brand names are used only to identify the equipment we service. Codes vary by model and model year — the legend on your own furnace is always the last word.
First — how to get the code out
There are two methods and you will need the second one more often than Daikin’s own instructions imply, because not every code appears in the scrolling list.
Method one: scroll and listen for the long beep
Hold the timer cancel button for five seconds. Two zeros flash on the temperature display. Press timer cancel repeatedly to step through the list. A short beep or two short beeps means keep going. A long beep means you have landed on your code.
Method two: search the two digits
Press temperature up, temperature down and mode at the same time. The left character blinks — step it with the arrows until you hear two beeps. Press mode, then do the same on the right character until you get a long beep. Daikin says outright that not all codes appear in method one, and that this is what you use when you cannot find yours.
Some handsets just show it
On certain remotes, holding timer cancel for five seconds puts the code straight onto the display with a long beep and no scrolling at all. If yours does this, you are done.
A green light on the board inside is not a fault
There is a small green indicator on the control board that blinks to show the processor is alive. It gets reported as a fault code regularly. It is the opposite.
What the codes mean
Refrigerant and electrical faults — not a homeowner job
Nothing on a Daikin carries a do-not-restart warning the way one Mitsubishi code does. But these are the ones where continuing to run it is doing damage rather than testing a theory.
U0
Refrigerant shortage
Daikin arrives at this three different ways — current against compressor speed, discharge pipe temperature, and the difference between suction and discharge. It is not automatically a leak; a faulty sensor or board can produce it. But it is a sealed-system diagnosis and opening that circuit legally requires EPA certification. Running a system that is genuinely short of refrigerant is hard on the compressor, so this is not one to live with.
F3 · F6
Discharge pipe temperature control, or high pressure in cooling
Both mean the system is running far outside where it should be. F6 is worth one outdoor check first — a coil packed with cottonwood or a unit boxed in by a fence will cause it. Beyond that it is refrigerant side.
E5 · E6 · E7
Compressor overload, compressor lock, or the outdoor fan locked
The compressor is drawing too much, has stopped turning, or the fan that cools it has stopped. Repeatedly resetting past any of these is the fastest way to turn a repair into a replacement.
Genuinely worth doing yourself first
One Daikin code is, more often than not, a filter.
A5
Freeze-up protection or heating peak-cut — the unit is protecting itself
Daikin’s own list of causes starts with short-circuited air and a clogged indoor filter, then dust on the indoor coil. In a house, it is usually the filter. Open the front flap, lift out the two mesh screens, wash them, let them dry properly and put them back. Also check nothing is blowing straight back into the unit — furniture, a curtain, or a shelf too close.
L3 · L4
The electrical box or the heat sink in the outdoor unit is getting too hot
Airflow around the outdoor unit. Leaves banked up against it, a shrub that has grown in, snow drifted around the base, or something stored in front of it.
U2
Low or high voltage detected
Worth checking the breaker before assuming the unit is at fault. Note how close this looks to U0 — they are one character apart and completely unrelated.
Needs a technician, but it is not an emergency
Sensors and boards, mostly.
U4
The indoor and outdoor units have stopped talking
Check the outdoor unit has power first. On multi-zone systems this code can mean the link to a branch box rather than to the outdoor unit, and communication with the outdoor unit is reported differently — which is one of several reasons a multi-zone chart is not the same as a single-zone one.
A1
Indoor control board fault
The board has found a problem with itself.
A6
Indoor fan motor
Worth knowing this presents almost identically to A5 from the sofa — the unit is not cooling properly — but A5 is a filter and A6 is a motor.
C4 · C9
Indoor coil thermistor, or room temperature thermistor
Small sensors, small parts.
E1
Outdoor control board fault
The outdoor equivalent of A1.
E8 · L5
Input overcurrent, or output overcurrent
The system is drawing more than it should. Usually points back at the compressor or the inverter.
EA
Four-way valve fault
The valve that flips the system between heating and cooling. A classic symptom is a heat pump that will do one and not the other.
H0 · H6 · H8 · H9 · J3 · J6 · P4
Sensors around the compressor and the outdoor coil
A cluster of thermistor and sensor faults. Individually small parts. H8 means different things depending on the capacity of your unit, which is one to leave to whoever has the model number in front of them.
Four ways a Daikin code gets read wrong
- Some codes only appear once the system has actually shut down. Daikin’s manual carries a footnote that is easy to miss: several codes, U0 among them, display only when the system goes down. So a unit that is limping along on low charge but still blowing something can be scrolled through the whole list without U0 ever appearing. That does not mean it is not the problem.
- U0 is not in the scroll list on older remotes at all. The code sequence differs by remote generation, and on one common older handset U0 is simply absent from it. If you have that remote, method two is the only way to reach it. This is not a fault, it is how the list was built.
- Aurora means two different things and one of them is commercial. The most widely circulated Daikin Aurora service manual online is actually for their commercial variable refrigerant flow equipment, where several codes mean genuinely different things than they do on a residential wall unit. If you find a chart through that route, it is the wrong chart.
- The scroll list is generic across the whole range. You can scroll to codes your unit has no hardware for. Seeing a code in the list does not mean your system supports it — only the long beep means anything.
Anything that involves refrigerant is not a do-it-yourself job, and that is federal law rather than our opinion
A good share of Daikin codes point at the sealed system, and U0 in particular is the one people most want to solve themselves after reading that it just needs a top-up. It does not just need a top-up. Refrigerant does not get used up, so a system that is short of it has lost it somewhere, and adding more without finding where is money poured into the ground. Opening a refrigerant circuit also legally requires EPA certification. What you genuinely can do is wash the filters, clear the outdoor coil, and make sure nothing has grown or drifted around the outdoor unit — and between them those cover a real share of the calls we take.
Got the long beep on a code?
Book it and put the two characters in the notes. On a Daikin the code narrows it down a long way before we arrive.
Book a Mini Split Diagnostic60 seconds online · or call (206) 486-6373
How it works when you book
- 1
Get the code before you cut the power On a mini split the code often lives in a recall mode that a power cycle wipes. Read it first.
- 2
Book online and tell us what it showed Takes about a minute. Say whether it was blinking on its own or you put it into a check mode.
- 3
You get the price before we start Diagnosed, explained, and quoted in writing. Nothing happens until you say go.
Our service areas
We run out of Covington and cover the greater Puget Sound area.
King County
Covington, Kent, Renton, Maple Valley, Auburn, Federal Way, Des Moines, Enumclaw, Bellevue, Issaquah, Sammamish, Bothell
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Tacoma, Puyallup, Lakewood, Sumner, Bonney Lake
Snohomish County
Lynnwood, Everett
Not on the list? We cover the greater Puget Sound area around our Covington base. Book it and a technician confirms within 1 business hour.
Why homeowners hand it to us
- You approve the price first. Upfront quote before a single screw turns.
- We answer 24/7. Book in a minute, hear from a technician within 1 business hour.
- 500+ jobs done by 4.9★ rated, professional technicians.
- Fixed right, guaranteed. If it’s not right, we make it right.
Quick answers
My unit shows a code but it is still running. Do I have to do anything?
Daikin says in its own literature that the system keeps operating even with a code showing, and that you should still get it checked. So there is usually no emergency. The exceptions are the compressor codes, where continuing to run it is what causes the damage rather than the original fault.
Where are the filters and how often should they be done?
Behind the flap on the front of the indoor unit. Lift the flap, slide the two mesh screens out, wash them in warm water, let them dry completely before they go back. Every couple of months in a normal house, more often with pets. It is the single highest-value thing you can do for a ductless system and it prevents the code that brings us out most.
What is the difference between U0 and U2?
Everything, despite them looking almost identical. U0 is refrigerant shortage and points at the sealed system. U2 is a voltage problem and points at the electrical supply. If you are reading a code off a small display in a dim room it is worth confirming which one you have before anyone starts quoting.
Do you work on Daikin if we did not buy it from you?
Yes. Daikin’s warranty asks for correct installation to code by a licensed contractor rather than a particular dealer. The one exclusion worth knowing about is equipment bought by a consumer over the internet, which Daikin treats differently.
Is a Daikin the same as a Goodman?
Same parent company, and Goodman furnaces and Daikin ductless are sold by the same organisation in the US. They are not the same equipment and they do not share a diagnostic system, so a Goodman furnace chart tells you nothing about a Daikin wall unit.
Tell us the code and we will know where to start.
Book online in about a minute. Put the two characters in the notes, and say whether the unit is still running.
Book a Mini Split Diagnostic60 seconds online · or call (206) 486-6373
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