E3 • Daikin • Altherma 4
Fault Code E3 Daikin Altherma 4: Causes, Diagnosis and Solution
E3 is a fault that may correspond to a protection or abnormal condition detected (depending on configuration). Diagnosis relies on context and readings.
Proof status : Manufacturer reference needed for the exact range
Source: Daikin documentation (installer/service manual – depending on product reference)
Founder, AskMarcel.app
Founder of AskMarcel.app. Sheets are written from manufacturer documentation; the reference is shown when it has been verified.
In brief
Fault code E3 on Daikin Altherma 4 means: E3 is a fault that may correspond to a protection or abnormal condition detected (depending on configuration). Diagnosis relies on context and readings. Most common cause: Protection triggered, inconsistent measurement, or abnormal event (depending on subsystem). First action: Note whether the fault occurs in heating, DHW, defrost, or standby.. Call a registered engineer if the fault returns after basic checks or involves refrigerant work (F-Gas registered engineer required).
According to Daikin's installer reference guides (FTJX AB9/AW9/AS9, AZQS B8V1/BY1, RZQG L9V1/L8Y1), the E3 fault code indicates activation of the high-pressure safety switch due to issues such as incorrect refrigerant level or blocked airflow.
Continue this diagnosis in Marcel
Daikin code E3: Marcel picks this code up for Altherma 4 and guides you, with the manufacturer reference when one exists.
For regular use on site: Install the app
What does fault code E3 on Daikin mean?
E3 is a fault that may correspond to a protection or abnormal condition detected (depending on configuration). Diagnosis relies on context and readings.
Protection triggered, inconsistent measurement, or abnormal event (depending on subsystem).
Symptoms
- Unit stops with code E3
- Fault after power increase
- Inconsistencies in readings
- Returns after reset
Diagnosis
1. Identify the triggering scenario
- Note whether the fault occurs in heating, DHW, defrost, or standby.
- Record key values just before the stop.
- Compare with the normal operating range.
2. Check sensors and wiring
- Inspect connectors and harness (poor contacts).
- Compare measurements with an external reference if possible.
- Check the environment (humidity, vibrations).
3. Apply the Daikin service procedure
- Follow the specific E3 procedure for the model.
- Perform recommended tests and confirm the cause.
- Validate after recommissioning over several cycles.
Repair and return to service — Daikin fault E3
Correction depends on the confirmed cause: wiring/sensor, or operating condition. Use the manufacturer's procedure to avoid unnecessary replacements and ensure safe recommissioning.
When should you call an F-Gas engineer?
Contact an F-Gas registered engineer if the fault returns after basic checks, involves refrigerant charging, or requires PCB or compressor replacement on Daikin Altherma 4.
Affected models
- FTXJ AB9
- FTXJ AW9
- FTXJ AS9
- AZQS B8V1
- RZQG L9V1
Field context
This fault occurs during commissioning or normal operation when the pressure in the refrigerant circuit exceeds the safety threshold. It is common in cases of incorrect stop valve adjustment, obstructed air intake/outlet filtration, gas overcharge, or fan failure.
Frequently asked questions
What does fault code E3 on the outdoor unit mean?
Fault code E3 indicates the high-pressure safety switch has been activated. This means the pressure in the circuit has exceeded the permitted limit. Possible causes include incorrect refrigerant level, blockages in the circuit or condenser, excessively high ambient temperature, or insufficient airflow. It is crucial to check these parameters before resetting.
Should I reset the E3 fault immediately?
No. The manufacturer's procedure requires that the fault only be reset after correcting the underlying cause. Resetting without intervention can lead to overheating or compressor damage. First check the refrigerant charge, absence of blockages, and fan operation.
What are the installation-related causes?
Manuals specifically cite installation errors such as closed stop valves or blocked air intake/outlet. Ensure valves are open and ventilation grilles are not obstructed. If the problem persists after checking the installation, inspect the compressor and pressure sensors.
Need help with this diagnosis?
Marcel reads your error codes and walks you through them step by step, with sourced answers.
Or keep going right now in your browser:
