Error F3 on Daikin FTXM25R Heat Pump | Causes & Fix

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• Source: Official Daikin service manual
• Reviewed by: Geo Technical Editorial
• Published: March 15, 2026
• Updated: March 15, 2026

Safety notice: Start with user-safe checks only. Do not open sealed refrigerant systems, inspect gas-train components, or work on energized high-voltage parts unless you are qualified to service this appliance.

Error F3 on Daikin : Outdoor discharge temperature sensor fault. Follow the troubleshooting steps below to diagnose and fix this heat-pump issue. ## What Error Code F3 Means on a Daikin FTXM25R Error F3 on the Daikin FTXM25R indicates the outdoor unit discharge temperature sensor is faulty. The discharge temperature sensor monitors the temperature of hot gas leaving the compressor. If this sensor reads outside the valid range (open-circuit or short-circuit), the control board cannot protect the compressor from overheating and raises F3. The sensor is located in the outdoor unit near the compressor discharge port. When F3 appears, the Daikin heat pump pauses normal operation to protect internal components from potential damage. Not every F3 fault requires a professional engineer — many are resolved through careful inspection and routine maintenance. Work through each diagnostic step below in sequence, starting with the simplest check, to identify the root cause efficiently before considering part replacement or arranging a service call. ## Symptoms - F3 on display

• System not operating
• Outdoor unit does not energise ## Common Causes - Outdoor discharge temperature sensor fault ## Tools You May Need - digital multimeter
• Phillips screwdriver ## Step-by-Step Repair Guide | Step | Action | Result | |------|--------|--------| | 1 | Isolate AC at the outdoor isolator. | Power isolated — continue to step 2 if the issue persists. | | 2 | Remove the outdoor unit service panel to access the compressor discharge area. | Panel removed — continue to step 3 if the issue persists. | | 3 | Locate the discharge temperature sensor (near the compressor top or discharge pipe). | Sensor located — continue to step 4 if the issue persists. | | 4 | Test sensor resistance: at 25 °C expect ~20–30 kΩ (Daikin discharge sensors are higher resistance than standard NTCs). OL or 0 Ω = faulty. | Resistance measured — continue to step 5 if the issue persists. | | 5 | Replace sensor. Restore power and test. | F3 cleared — if the fault remains, contact a qualified technician. | ## Safety Precautions Always isolate the outdoor unit at both the main circuit breaker and the outdoor unit isolator before accessing internal components. The outdoor unit operates at mains voltage. ## Estimated Repair Time and Difficulty Most heat pump error code F3 faults can be assessed and addressed in 30–90 minutes using the steps above. The diagnostic process requires only basic tools: a multimeter and standard screwdrivers cover the majority of checks described here. If a replacement part is required, allow 1–5 working days for delivery. A trained technician with access to the correct diagnostic equipment will typically resolve this type of fault within a single service visit. ## When to Call a Technician Contact a Daikin authorised service technician if: the fault persists after following all the steps above; if PCB-level or refrigerant-circuit work is required; or if you are not comfortable working with electrical or mechanical components. When calling, have the full model number, the error code displayed, and a brief description of any sounds or symptoms you noticed before the fault appeared — this helps the technician prepare the correct parts and tools. ## Frequently Asked Questions Q: Is F3 a DIY repair? Locating and replacing the discharge sensor requires opening the outdoor unit electrical compartment, which operates at mains voltage. This should be done by a qualified engineer. Q: Can F3 cause compressor damage? Yes — without the discharge sensor, the control board cannot protect the compressor from high-temperature discharge. Address F3 promptly. Q: How is the discharge temperature sensor different from other NTCs? Discharge temperature sensors are rated for higher temperatures (up to 150+ °C) and typically have a higher base resistance than standard room or coil NTCs. ### Is it safe to keep using my Daikin with error F3? If error F3 does not indicate an immediate safety hazard such as a gas leak, electrical short, or water flooding, you can continue limited use while monitoring the appliance. However, running the heat-pump with an active error code increases the risk of further damage. Address the underlying issue as soon as possible. For high-severity errors, disconnect the appliance and contact a qualified technician. ### How much does it cost to fix error F3 on a Daikin ? Repair costs for error F3 on the Daikin heat-pump depend on the root cause. DIY fixes such as cleaning filters, resetting the unit, or reconnecting loose wires cost nothing beyond basic tools. If a component replacement is needed, parts and labor from a certified technician are the main expenses. Contact a Daikin-authorized service provider for an accurate estimate based on your specific situation. ### What does error code F3 mean on a Daikin heat-pump? Error code F3 on Daikin heat-pump models indicates Outdoor discharge temperature sensor fault. This error is detected by the appliance’s internal diagnostic system and displayed to alert the user that attention is needed. Refer to the troubleshooting steps above for guidance on resolving this issue. ### Is it safe to keep using my Daikin with error F3? If error F3 does not indicate an immediate safety hazard such as a gas leak, electrical short, or water flooding, you can continue limited use while monitoring the appliance. However, running the heat-pump with an active error code increases the risk of further damage. Address the underlying issue as soon as possible. For high-severity errors, disconnect the appliance and contact a qualified technician. ### How much does it cost to fix error F3 on a Daikin ? Repair costs for error F3 on the Daikin heat-pump depend on the root cause. DIY fixes such as cleaning filters, resetting the unit, or reconnecting loose wires cost nothing beyond basic tools. If a component replacement is needed, parts and labor from a certified technician are the main expenses. Contact a Daikin-authorized service provider for an accurate estimate based on your specific situation. ### What does error code F3 mean on a Daikin heat-pump? Error code F3 on Daikin heat-pump models indicates Outdoor discharge temperature sensor fault. This error is detected by the appliance’s internal diagnostic system and displayed to alert the user that attention is needed. Refer to the troubleshooting steps above for guidance on resolving this issue.