Daikin E1-00 Fault Code: Causes, Fixes & Repair Costs
What does the Daikin E1-00 fault code mean?
The E1-00 code on a Daikin heat pump signals a fault with the outdoor unit's printed circuit board (PCB) — the control board that orchestrates the compressor, fan motor, and all other outdoor-unit functions. When this board fails or loses reliable communication, the system locks out and will not run until the underlying problem has been identified and resolved. The sub-code 00 indicates a significant system-level fault rather than a minor sensor glitch, so the unit needs professional attention if a simple power cycle does not clear it.
General guidance only — not a substitute for professional advice, and not certified by an heat pump engineer. Always have your specific appliance assessed by a qualified professional. Any heat pump work must be carried out by an MCS-certified heat pump engineer. If you notice a refrigerant leak, a burning smell or water leaking from the unit, switch it off at the isolator and call an MCS-certified heat pump engineer. Refrigerant work must be carried out by an F-Gas registered engineer.
Common causes
- Faulty or damaged outdoor PCB Common
The circuit board itself has developed a hardware fault — a burned component, a cracked solder joint, or a failed driver chip. This is the most common root cause when E1-00 returns immediately after every reset and does not clear with a power cycle.
- Electrical noise or voltage spike Common
A mains power surge or transient voltage spike can overwhelm the PCB's protection circuitry and throw an E1-00 code. In some cases the fault is a one-off glitch that clears after a full power cycle at the isolator, with no lasting board damage.
- Loose or corroded wiring and connectors Sometimes
Corroded terminals or connectors that have worked loose — particularly on the harness running to the outdoor PCB — can produce intermittent signals that the board interprets as a failure. This can closely mimic a genuine board fault on diagnostics.
- Blocked airflow causing outdoor unit overheating Sometimes
Leaves, debris, overgrown vegetation, or snow packed around the outdoor unit restrict airflow through the coil. Sustained high temperatures inside the unit can trigger PCB thermal-protection faults and log an E1-00 code.
- Secondary component damage Rare
If E1-00 has been ignored for a period or the unit has been repeatedly reset through a persistent fault, secondary damage to the compressor or other components can develop. In this scenario the PCB may itself be damaged by an upstream component failure rather than being the original cause.
How to fix it
- Switch the unit off at the outdoor isolator — not just from the controller or app DIY safe
Use the dedicated isolator switch near the outdoor unit rather than the indoor controller. This ensures a full power removal from the outdoor PCB. Wait at least five minutes before switching back on, allowing the inverter capacitors to fully discharge.
- After restoring power, allow two minutes for the system to complete its start-up handshake before calling for heat DIY safe
Watch the controller display. If E1-00 does not return within the first hour of operation, the fault was most likely a transient electrical glitch. Do not attempt more than two full power cycles — repeated resets through a genuine fault can cause additional damage.
- Inspect the area around the outdoor unit and clear any obstructions DIY safe
Check for leaves, debris, overgrown plants, or compacted snow blocking the intake or discharge grilles. Leave at least 30 cm of clear space on all sides. Do not use a pressure washer — gentle removal by hand or a soft brush is sufficient.
- Check that the main consumer unit MCB for the heat pump circuit has not tripped DIY safe
Go to your consumer unit (fuse board) and confirm the MCB labelled for the heat pump is in the ON position. If it has tripped, reset it once. If it trips again immediately, do not reset it a second time — this indicates an electrical fault requiring an engineer.
- If E1-00 returns after a power cycle, switch the system off and contact an MCS-certified heat pump engineer heat pump engineer
A persistent E1-00 means the outdoor PCB or an associated component needs hands-on diagnosis with specialist tools. Leave the system switched off to avoid further damage. The engineer will inspect all wiring harnesses and connectors, test the PCB under load, and determine whether the board can be repaired or needs replacing with a genuine Daikin part. Any work involving the refrigerant circuit also requires an F-Gas registered engineer.
Parts you may need
- Daikin outdoor unit PCB (main inverter control board) · from £320
- Wiring harness / connector kit for outdoor unit · from £45
- Outdoor unit PCB fuse set · from £12
- Surge protection device (SPD) for heat pump supply · from £55
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £350–£900, depending on the underlying cause.
Frequently asked questions
Can I fix Daikin E1-00 myself?
The only safe DIY actions are a full power cycle at the isolator, clearing debris from around the outdoor unit, and checking your consumer unit for a tripped MCB. Everything beyond that — inspecting the PCB, testing wiring, replacing components — must be done by an MCS-certified heat pump engineer. Working inside the outdoor unit without the right training and tools risks electric shock and can make the fault significantly worse.
How much does it cost to fix Daikin E1-00 in the UK?
Most repairs that trigger an E1-00 code cost between £350 and £900 all-in, including parts and labour. A minor wiring or connector fix sits at the lower end of that range, while a full PCB replacement typically falls between £450 and £900 depending on the model and the engineer's call-out rate. In rare cases where the PCB fault has caused secondary damage — for example to the compressor — costs can rise significantly above £900, sometimes exceeding £1,400. An engineer's diagnosis will tell you which scenario you are dealing with before you commit to a repair.
Will my Daikin warranty cover an E1-00 PCB fault?
It may do. Daikin's standard residential warranty covers manufacturing defects on parts for three years from installation. If the PCB has failed due to a manufacturing defect within that window, and the unit has been serviced annually by an F-Gas certified engineer, Daikin should cover the replacement part. Keep all service records — without them Daikin can decline the claim. Damage caused by a mains power surge or installer error may not be covered, so check with your installer and your home insurance policy.
Is it safe to keep running the heat pump while E1-00 is showing?
No. Once E1-00 appears and does not clear after one or two power cycles, you should leave the system switched off. Continuing to attempt restarts through a genuine PCB or electrical fault can cause further damage to the compressor and other components, potentially turning a £500 repair into a much more expensive one. Switch the system off at the isolator and arrange for an engineer as soon as possible, especially during cold weather when you need heating.