Daikin Altherma Heat Pump Problems — Fault Codes & Fixes
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Post a job — we'll find you an engineer →Daikin Altherma refrigerant faults must be investigated by an F-Gas certified engineer. Do not attempt to access the outdoor unit internals.
The Daikin Altherma is a solid choice for UK homes switching to renewable heating, but like any heat pump, it can throw fault codes that leave you scratching your head. Most problems fall into two camps: refrigerant pressure issues (which need a qualified engineer) and electrical faults (which sometimes respond to a simple restart). This guide walks through the most common fault codes you'll encounter—7H, A1, E3, and EA—and explains what's happening behind the scenes. You'll learn which problems you can safely investigate yourself and which demand a call to a professional. Understanding these codes can save you money on unnecessary engineer call-outs and keep your system running smoothly through the winter.
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Most likely cause & what to check
The Daikin Altherma is one of the UK's most popular air source heat pump ranges — available as low-temperature (R32) and high-temperature models, and in split and monobloc configurations. It is widely regarded as a reliable and well-supported product. Manuals and fault code guides are at daikin.co.uk or call Daikin UK technical support on 0845 641 9000.
Fault code 7H (high discharge pressure): the refrigerant pressure in the outdoor unit has exceeded safe limits. Common causes include a dirty or obstructed outdoor unit coil (check for debris), a refrigerant overcharge, or a failing expansion valve. This is an F-Gas engineer job — do not reset repeatedly.
Fault code A1 (PCB fault — indoor unit): the printed circuit board in the indoor unit has detected a fault. Power-cycle the system once (isolator off for 5 minutes, then on). If A1 returns, the PCB or a connected sensor has failed — an engineer needs to diagnose which.
Fault code E3 (high pressure protection): similar to 7H — the system has shut down to prevent overpressure. Check the outdoor unit airflow is not restricted. If clear, an F-Gas engineer should check refrigerant charge and the high-pressure switch.
Fault code EA (refrigerant leak detected): the Altherma has an internal refrigerant leak detection feature on some models. If EA appears, do not continue running the system — contact your installer or Daikin UK immediately. Refrigerant R32 is mildly flammable.
Daikin Altherma warranty: 5-year parts and labour warranty when installed by a Daikin D1 or D2 registered installer. Registration required within 30 days at daikin.co.uk/warranty. Daikin have their own engineer network in the UK for warranty repairs.
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Frequently asked questions
Can I reset my Daikin Altherma fault code myself?
Yes, but only once—power-cycle the system by switching the isolator off for 5 minutes and back on. This often clears temporary electrical glitches like fault code A1. However, if the fault returns immediately, the underlying problem needs professional diagnosis; repeatedly resetting masks the real issue and wastes your time.
What should I do if my heat pump displays fault code EA (refrigerant leak)?
Stop using the system immediately and contact your installer or Daikin UK technical support on 0845 641 9000. R32 refrigerant is mildly flammable, and a leak must be located and sealed by an F-Gas certified engineer before the system can safely restart.
How do I know if my outdoor heat pump unit is blocked or dirty?
Visually inspect the outdoor unit's coil fins for leaves, cobwebs, mud, or ice buildup, especially after winter storms or near trees. Gently remove any loose debris with your hands or a soft brush, but do not use a pressure washer or force anything inside—that's a job for a technician if deep cleaning is needed.
Is a Daikin Altherma fault code covered by warranty?
Yes, if your system was installed by a registered Daikin D1 or D2 installer and you registered for the 5-year parts and labour warranty within 30 days of installation. Check your paperwork or log in to daikin.co.uk/warranty; if you're covered, Daikin's own engineer network will handle the repair at no cost.
What's the difference between fault codes 7H and E3?
Both relate to high refrigerant pressure, but 7H specifically indicates the discharge pressure has exceeded safe limits (usually caused by debris or overcharge), whilst E3 is the system's protective shutdown to prevent damage. Both require an F-Gas engineer to diagnose and fix—they're not DIY problems.