In brief
Fault code F3 on Daikin Altherma 4 means: F3 generally corresponds to a triggered protection or an inconsistent measurement on a sensor/input. The aim is to identify the affected area via the history and readings. Most common cause: Typical causes: faulty sensor, wiring/connection, or an actual condition causing protection (depending on the circuit). First action: Identify the exact moment F3 appears (start-up, DHW, defrost).. Call a registered engineer if the fault returns after basic checks or involves refrigerant work (F-Gas registered engineer required).
According to Daikin manuals, the F3 code on Altherma 4 units can result from excessive temperature of the R2T discharge sensor on the compressor, a faulty sensor, a damaged connection cable, or a failing compressor.
F3 • Daikin • Altherma 4
Fault Code F3 Daikin Altherma 4: Diagnosis (Sensor / Protection)
F3 generally corresponds to a triggered protection or an inconsistent measurement on a sensor/input. The aim is to identify the affected area via the history and readings.
Source: Daikin documentation (installer/service manual – according to product reference)
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What does fault code F3 on Daikin mean?
F3 generally corresponds to a triggered protection or an inconsistent measurement on a sensor/input. The aim is to identify the affected area via the history and readings.
Typical causes: faulty sensor, wiring/connection, or an actual condition causing protection (depending on the circuit).
Symptômes
- Safety shutdown
- F3 displayed after load increase
- Inconsistent temperature/pressure in readings
- Short cycling
Diagnostic
1. Read the history and take measurements
- Identify the exact moment F3 appears (start-up, DHW, defrost).
- Record available measurements (temperatures, pressures, states).
- Spot an anomalous value correlated with the fault.
2. Check sensor and wiring/connection
- Visually inspect the suspected sensor (fixing, cable).
- Check connectors (oxidation, loose contact).
- If possible, verify sensor consistency with an external measurement.
3. Apply the manufacturer's procedure
- Follow the Daikin procedure corresponding to F3 for the exact reference.
- Perform the recommended checks and validate the correction on restart.
- Document the intervention (before/after measurements).
How to reset fault code F3 on Daikin?
An F3 is often resolved by restoring a sensor/connection or by correcting the condition that triggers the protection. To avoid unnecessary replacement, validate the hypothesis through measurements and procedure.
When should you call an F-Gas engineer?
This code appears when the outdoor unit detects an abnormally high refrigerant temperature at the compressor discharge or discharge pipe. It often occurs during heating cycles or mode reversal, particularly if ventilation is obstructed, if the refrigerant level is incorrect, or if the ambient temperature is outside the operating range.
Affected models
- FTXJ AB9, FTXJ AW9, FTXJ AS9
- RXYSQ TV9, RXYSQ TY9, RXYSQ T8V, RXYSQ T8Y
- 4MWXM A9
- EHSH B, EHSHB B, EHSX B, EHSXB B
- 3MXM N, 3AMXM M, 3AMXF A, 3MXF A, 4MXM N, 5MXM N
Field context
This code appears when the outdoor unit detects an abnormally high refrigerant temperature at the compressor discharge or discharge pipe. It often occurs during heating cycles or mode reversal, particularly if ventilation is obstructed, if the refrigerant level is incorrect, or if the ambient temperature is outside the operating range.
Technical source data
The F3 code on Daikin Altherma 4 units indicates evaporator overheating or a discharge pipe temperature malfunction. According to the manuals, this can result from excessive temperature of the R2T discharge sensor on the compressor, a faulty sensor, a damaged connection cable, or a failing compressor. In some contexts, this code also signals compressor thermal protection related to insufficient ventilation, clogged filters, incorrect refrigerant pressure, or unsuitable ambient temperature. Resolution requires checking the R2T sensor condition, connection integrity, and compressor operating conditions before considering replacement (FTXJ AB9/FTXJ AW9/FTXJ AS9, RXYSQ TV9/RXYSQ TY9/RXYSQ T8V/RXYSQ T8Y, 4MWXM A9, EHSH B/EHSHB B/EHSX B/EHSXB B, 3MXM N/3AMXM M/3AMXF A/3MXF A/4M
Sources: FTXJ AB9.FTXJ AW9.FTXJ AS9 Installer reference guide 4PFR769827 6C French — ftxj-ab9-ftxj-aw9-ftxj-as9-installer-reference-guide-4pfr769827-6c-french.pdf (p. 55) · RXYSQ TV9,RXYSQ TY9,RXYSQ T8V,RXYSQ T8Y 4PFR482275 1B Installation and operation manual French — rxysq-tv9-rxysq-ty9-rxysq-t8v-rxysq-t8y-4pfr482275-1b-installation-and-operation-manual-french.pdf (p. 14) · 4MWXM A9 Installer reference guide 4PFR708645 1A French — 4mwxm-a9-installer-reference-guide-4pfr708645-1a-french.pdf (p. 73)
Questions fréquentes
What are the main causes of an F3 code on an Altherma 4?
The F3 code primarily signals evaporator overheating or a malfunction of the discharge pipe temperature. Identified causes include a faulty R2T discharge temperature sensor, a defective connection cable, or a failing refrigerant compressor. It can also be a compressor thermal protection triggered by insufficient ventilation.
How to diagnose and resolve an F3 code?
To resolve this fault, start by checking the condition of the R2T discharge temperature sensor and its connection cable. If these are valid, inspect the outdoor unit ventilation, air filters, and refrigerant level. Also check the ambient temperature. If the R2T sensor displays an incorrect value compared to ambient temperature, replace it. In case of doubt, follow the manufacturer's procedure.
Is the F3 code related to burn damage?
Although the F3 code is specifically associated with evaporator overheating or a discharge pipe malfunction, it can appear in scenarios including burn damage if a short circuit in the power circuit or a loose connection has damaged components. However, the standard procedure for F3 focuses on checking sensors and connections.
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