Daikin E3 fault codewhat it means and how to fix it
The outdoor unit’s high pressure switch has opened. Daikin list a closed stop valve, a faulty sensor or switch, overcharge, moisture, a blockage and the fan, and require a manual reset.
Take care
Get an F-Gas certified heat pump engineer to look at your Daikin E3
We do not pass enquiries to a repair firm, so there is no form here. When you book an F-Gas certified heat pump engineer, tell them the make, the model and the exact code or message on the display, and ask whether they carry parts for this make — that is what turns one visit into a repair rather than a quote.
What E3 means
E3 is "OU: Actuation of high pressure switch" in Daikin’s Altherma table, and the service manual describes the trigger precisely: the switch opens because the measured pressure has risen above its operating point. There is a second, quieter route to the same code — if high pressure control, where the pressure sits just below the switch point, occurs sixteen times within three hundred minutes, the unit declares E3 anyway. Either way the unit stops, and the reset is manual, at the user interface. The suffix matters. E3-00 is the switch actuating. E3-24, which appears in the Altherma 3 M table, is listed there as "High pressure sensor abnormality" and headed "High pressure switch abnormality" in the service manual, and its checklist drops the stop valve check and starts with the pressure sensor: a diagnosis pointing at the component rather than the pressure.
Daikin’s checklist for the engineer runs: stop valves on the refrigerant circuit fully open; the refrigerant pressure sensor; the high pressure switch; the main PCB; whether the circuit is overcharged; non-condensables or moisture in the circuit; a clogged circuit; and the outdoor unit fan motor. Notice what that list is about — the refrigerant side and the fan — which is why this is a code for an F-Gas certified engineer rather than a heating engineer.
What an owner can bring is context. If it appeared on a hot day, during the hot water cycle or when the outdoor unit was boxed in by something, say so. And if your controller shows E33, read the code again from the Malfunctioning menu rather than the home screen banner: Daikin’s tables have no E33, and the outdoor unit high pressure code is E3 with a two-digit detail code after it.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Stop valve not fully open | Daikin’s first check. A valve left partly closed at commissioning restricts the circuit and pressure climbs on the high side. | Common |
| Pressure sensor or high pressure switch faulty | Daikin’s second and third checks. E3-24 on the Altherma 3 M names the component rather than the pressure: sensor in the installer guide, switch in the service manual heading. | Common |
| Overcharge, moisture or a blockage in the circuit | Three items on Daikin’s list that all raise head pressure. Every one is inside the sealed refrigerant circuit. | Occasional |
| Outdoor unit fan not moving enough air | Daikin’s final check is the fan motor. In cooling mode the outdoor coil is where the heat goes, and a fan that is failing or a coil that is boxed in lets pressure build. | Occasional |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£120–£800
Time on site
15 minutes
A diagnostic visit from an F-Gas certified engineer is typically £120 to £250. A stop valve adjustment or a switch replacement stays near the bottom; recovering and recharging an overcharged or contaminated circuit, or a fan motor, takes it higher.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Daikin fault codes
- U0Get it checkedShortage of refrigerant in the Altherma outdoor unit. Daikin’s own checklist ends with a leak test, the circuit is sealed, and on an R32 unit this is F-Gas certified work by law.Related: refrigerant circuit
- H4Get it checkedMalfunction of the low pressure switch, a protection device on the refrigerant side of the outdoor unit. Daikin publish the name and nothing an owner can act on; it is certified work.Related: refrigerant circuit
- Bill has jumpedGet it checkedThe most important heat pump fault has no code. If your electricity cost has stepped up with no change in habits, the backup heater is probably doing the work.Related: same brand
- Ice on the outdoor unitGet it checkedNormal in cold damp weather, and the unit clears it itself. Daikin specifically forbid helping — no hot water, no de-icer, no scraping.Related: same brand
- 7HGet it checkedA water flow problem. The sub-code matters more than the code: 7H-01 clears itself, 7H-04 to 7H-06 need a manual reset, 7H-08 is the pump, and 7H-07 is the unit freeing a stuck pump.Related: same brand
- Water at the tap is too coldGet it checkedDaikin give two causes and a remedy that costs money. Before using it, check what your schedule is actually asking the cylinder to do.Related: same brand
Own a Daikin heat pump? Save it and its codes come first next time.
Related guides
Common questions about Daikin E3
My display says E33, not E3. What is E33?
Daikin’s published Altherma tables have no E33. The outdoor unit high pressure code is E3, shown with a two-digit detail code such as E3-00 or E3-24, and a banner that has run the two together is the likeliest explanation. Open the Malfunctioning menu and read the full code there.
Is E3 the same on a Daikin air conditioner?
The headline is similar — Daikin splits also report high pressure under the E family — but this page is written around the Altherma’s outdoor unit and the service manual for it. For a wall-mounted air conditioner, use the Daikin pages in our air-conditioning section.
Why did it happen when nothing seemed wrong?
Possibly because of the sixteen-in-three-hundred-minutes rule. Daikin declare E3 if high pressure control — pressure hovering just under the switch point — happens sixteen times in five hours, even if the switch never actually opens. That is a unit working hard against something, and the engineer’s list will find what.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.