What causes Daikin Mini Split E1?

A one-time glitch from electrical noise, a momentary voltage drop or a brief power failure that upset the outdoor board's microcontroller. Daikin lists this first, and a power reset clears it. Damaged EEPROM memory on the outdoor unit PC board (A1P on SkyAir units). A faulty outdoor unit PC board. A broken wiring harness between the boards inside the outdoor unit. A poor connection on the relay (interconnecting) wires between the indoor and outdoor units, per Daikin's Simple Self-Diagnosis list. An outdoor unit that isn't properly grounded, which Daikin's Entra flowchart checks before replacing the board.

How do I fix Daikin Mini Split E1?

Turn the system off, then switch off the breaker or outdoor disconnect for the outdoor unit. Wait a few minutes and turn it back on. Daikin's first troubleshooting step for E1 on both SkyAir and Entra units is simply to cycle the power. If the unit runs normally afterward, Daikin treats it as an outside factor such as noise or a power blip, not a failed part. Note when it happened (storm, generator, brownout) in case it repeats. If E1 shows up after storms or power outages, consider having a surge protective device installed on the HVAC circuit by an electrician. Look at the outdoor unit from the outside only: check for obvious damage, pests nesting in the unit, or a disconnect box that has been knocked loose. Don't open the electrical cover. If E1 comes back after a power reset, stop resetting and call a licensed HVAC technician. The remaining checks are inside the outdoor unit's electrical box.

When should I call a pro for Daikin Mini Split E1?

Following Daikin's Entra flowchart: confirming the error returns after power is restored, then checking that the outdoor unit is properly grounded and correcting the ground if it isn't. Inspecting the harness between the outdoor PC boards and replacing it if it's broken; if the harness is good, replacing the outdoor PCB. On SkyAir units per SiUS25-501, replacing the outdoor unit main PC board (A1P) when E1 doesn't clear after a power reset. Checking the indoor-outdoor relay wiring and terminal connections, a cause in Daikin's Simple Self-Diagnosis list. Ordering the replacement board by the exact outdoor unit model number, since Daikin boards are model-specific.

Code: E1🔧 Daikin Mini Split

Daikin Error Code E1: Outdoor Unit PC Board Abnormality (Meaning, Causes, Fixes)

Q: What does Daikin Mini Split E1 mean?

E1 on a Daikin air conditioner or heat pump points at the outdoor unit's control board. Daikin says the board couldn't read its own memory (EEPROM) correctly, which can come from electrical noise or a momentary power dip, a damaged board, or a broken wiring harness between boards. Turn the power off at the breaker and back on once. If E1 returns, a technician checks grounding and the harness, and replaces the outdoor board if those are fine. Daikin's SkyAir inverter service manual SiUS25-501 titles E1 "Outdoor Unit: PC Board Defect" and lists it as "PC board defect, E2PROM defect" for all outdoor unit models. The outdoor board checks data from its E²PROM, a type of memory that keeps its contents with the power off, and sets E1 when that data can't be read correctly. The service manual for Daikin's Entra wall-mount mini splits (FTK(X)B/RK(X)B) calls E1 "Outdoor PCB abnormality" and gives four root causes: the board's microcontroller running away because of noise, a momentary voltage drop or power failure; a damaged EEPROM; a faulty outdoor board; or a broken harness between boards. Daikin's Simple Self-Diagnosis list also names a defective connection of the indoor-outdoor relay wires. Don't confuse it with A1, which is the indoor board on these systems.

Reviewed 2026-10-24 · Based on 3 manufacturer & service sources

What the code means

Daikin's SkyAir inverter service manual SiUS25-501 titles E1 "Outdoor Unit: PC Board Defect" and lists it as "PC board defect, E2PROM defect" for all outdoor unit models. The outdoor board checks data from its E²PROM, a type of memory that keeps its contents with the power off, and sets E1 when that data can't be read correctly. The service manual for Daikin's Entra wall-mount mini splits (FTK(X)B/RK(X)B) calls E1 "Outdoor PCB abnormality" and gives four root causes: the board's microcontroller running away because of noise, a momentary voltage drop or power failure; a damaged EEPROM; a faulty outdoor board; or a broken harness between boards. Daikin's Simple Self-Diagnosis list also names a defective connection of the indoor-outdoor relay wires. Don't confuse it with A1, which is the indoor board on these systems.

Likely causes

A one-time glitch from electrical noise, a momentary voltage drop or a brief power failure that upset the outdoor board's microcontroller. Daikin lists this first, and a power reset clears it.
Damaged EEPROM memory on the outdoor unit PC board (A1P on SkyAir units).
A faulty outdoor unit PC board.
A broken wiring harness between the boards inside the outdoor unit.
A poor connection on the relay (interconnecting) wires between the indoor and outdoor units, per Daikin's Simple Self-Diagnosis list.
An outdoor unit that isn't properly grounded, which Daikin's Entra flowchart checks before replacing the board.

Safe DIY checks

⚠ Before you start

Switch off the breaker and outdoor disconnect before anyone opens the outdoor unit; Daikin says to turn the power off before connecting or disconnecting any connector, and inverter boards can hold a dangerous charge after power is removed. Board, harness and grounding work should be done by a qualified technician or electrician.

Turn the system off, then switch off the breaker or outdoor disconnect for the outdoor unit. Wait a few minutes and turn it back on. Daikin's first troubleshooting step for E1 on both SkyAir and Entra units is simply to cycle the power.
If the unit runs normally afterward, Daikin treats it as an outside factor such as noise or a power blip, not a failed part. Note when it happened (storm, generator, brownout) in case it repeats.
If E1 shows up after storms or power outages, consider having a surge protective device installed on the HVAC circuit by an electrician.
Look at the outdoor unit from the outside only: check for obvious damage, pests nesting in the unit, or a disconnect box that has been knocked loose. Don't open the electrical cover.
If E1 comes back after a power reset, stop resetting and call a licensed HVAC technician. The remaining checks are inside the outdoor unit's electrical box.

🛠 When to call a pro

Following Daikin's Entra flowchart: confirming the error returns after power is restored, then checking that the outdoor unit is properly grounded and correcting the ground if it isn't.
Inspecting the harness between the outdoor PC boards and replacing it if it's broken; if the harness is good, replacing the outdoor PCB.
On SkyAir units per SiUS25-501, replacing the outdoor unit main PC board (A1P) when E1 doesn't clear after a power reset.
Checking the indoor-outdoor relay wiring and terminal connections, a cause in Daikin's Simple Self-Diagnosis list.
Ordering the replacement board by the exact outdoor unit model number, since Daikin boards are model-specific.

Parts that commonly fix it

Always match the part number to your exact model.

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Outdoor control board

Daikin's fix when E1 keeps returning and grounding and the harness check out; order by your outdoor unit model number.

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Multimeter

For a technician checking the ground and wiring continuity before replacing the board.