- Heat pumps
- Air-to-water heat pump
L4-07
Daikin Altherma 4 H F L4-07: fan 2 radiation fin overheating
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
When L4-07 appears on a Daikin Altherma 4 H F, the outdoor unit has halted heat pump operation because the fan 2 radiation fin exceeded its temperature limit. Review [11] Malfunction history for P4-03, check exterior airflow clearance, and contact your installer.
Safety first
Stop and check this first
- Never open the outdoor unit switch box yourself. High-voltage capacitors inside the inverter circuit require disconnecting all power for more than 10 minutes and verifying less than 50 V DC before any contact.
- Do not bypass thermal protections or cycle external power switches to force L4-07 to clear; Daikin prohibits external switching timers and requires identifying the overheating cause before resetting.
Safe checks you can perform
- Check [11] Malfunctioning and Malfunction history for P4-03 or L3-00 next to L4-07
- Check outdoor ambient temperature in [6.3] Sensors against the operating envelope
- Verify from outside that the outdoor unit ventilation path is unobstructed
- Verify backup heating in [5.23] Emergency selection and contact the installer in [6.2]
Leave these tasks to a qualified professional
- Do not attempt this professional task: De-energize for 10 minutes, verify <50 V DC, and test the fan 2 fin thermistor and heatsink
- Do not attempt this professional task: Correct the fan 2 fin cooling or PCB fault, execute the manual reset, and log a load test
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
De-energize for 10 minutes, verify <50 V DC, and test the fan 2 fin thermistor and heatsink
What they doA Daikin certified technician must shut off all power supplies, wait more than 10 minutes, confirm less than 50 V DC at the main circuit capacitors, and inspect the fan 2 radiation fin, thermal compound, and P4-03 thermistor harness.
They must show youthe voltmeter confirmation below 50 V DC after 10 minutes and the ohmmeter measurement of the fan 2 fin temperature sensor.
In writingthe measured capacitor voltage (V DC), the fan 2 thermistor resistance (ohms) versus temperature (°C), and the condition of the fan 2 radiation fin.
Correct the fan 2 fin cooling or PCB fault, execute the manual reset, and log a load test
What they doAfter repairing the fan 2 heatsink cooling path, thermistor, or inverter PCB according to the service manual, the technician must manually reset L4-07 and run the heat pump under load while observing fin temperature.
They must show youthe stable fan 2 radiation fin temperature during compressor and fan operation and a clean [11] Malfunction history log.
In writingthe verified cause of L4-07, any replaced part references, and the duration and temperature readings of the post-reset test run.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Check [11] Malfunctioning and Malfunction history for P4-03 or L3-00 next to L4-07
- Who:
- You operating the indoor user interface with permission set to advanced end user.
- How:
- Go to [11] Malfunctioning, tap the L4-07 entry to display its long description, and check [11]: Malfunction history for companion codes P4-03 (Fan 2 fin temperature sensor error), L4-06, or L3-00.
- Result that matters:
- Whether the controller also detected a fan 2 fin thermistor abnormality or broader outdoor switch box heat.
- If P4-03 is present in the malfunction history near L4-07, that points to the fan 2 fin temperature sensor or its wiring as the primary suspect.
- If L4-07 appears without P4-03, that rules out a direct open/short sensor code and suggests actual heat buildup on the fan 2 radiation fin.
- Evidence to keep:
- Photograph the [11] Malfunctioning help text and the recent malfunction history log showing dates and times.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C · Daikin Altherma 4 H F+W+ECH2O operation manual 4PEN773378-1C
Check outdoor ambient temperature in [6.3] Sensors against the operating envelope
- Who:
- You checking the status menus on the indoor touchscreen after the L4-07 stop.
- How:
- Open [6.3] Information > Sensors to view the outside temperature and leaving water temperature, and note which operation mode was active in [6.5] Operation modes.
- Result that matters:
- Whether the outdoor unit was running inside Daikin's specified ambient limits (-28~25°C for heating, 10~43°C for cooling, up to 40°C for domestic hot water).
- If the outside temperature reading exceeded 43°C in cooling or 40°C during tank heating, that indicates operation outside design ambient limits triggered L4-07.
- If the outside temperature was moderate when L4-07 stopped the heat pump, that rules out weather extremes and points to the fan 2 cooling path or inverter electronics.
- Evidence to keep:
- Write down the [6.3] sensor readings and the active mode shown in [6.5] before calling for service.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C · Daikin Altherma 4 H F+W+ECH2O operation manual 4PEN773378-1C
Verify from outside that the outdoor unit ventilation path is unobstructed
- Who:
- You inspecting the exterior of the outdoor unit without opening any covers or touching fins.
- How:
- Walk around the outdoor unit to confirm that nothing rests on the top panel, the surrounding space is clean, and no leaves, snow, or enclosures block the air inlet or fan discharge.
- Result that matters:
- Unrestricted air circulation across the outdoor heat exchanger and internal switch box cooling passage.
- If an external cover, vegetation, or stored item was blocking the unit, clearing it from outside confirms a ventilation bottleneck that must be reported to the technician.
- If all sides of the outdoor unit are clean and open, that rules out exterior airflow obstruction as the cause of L4-07.
- Evidence to keep:
- Keep a dated photograph of the outdoor unit exterior and surrounding clearance.
Do not open the outdoor unit or touch the aluminium fins; the cabinet houses live inverter voltage and flammable R290 refrigerant.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C · Daikin Altherma 4 H F+W+ECH2O operation manual 4PEN773378-1C
Verify backup heating in [5.23] Emergency selection and contact the installer in [6.2]
- Who:
- You at the indoor controller while the outdoor unit remains stopped on L4-07.
- How:
- Do not attempt to clear the manual L4-07 lockout; instead, check [5.23] Settings > Emergency selection to see how the electrical heater handles space heating and hot water during a heat pump failure, and read the contact number in [6.2] Dealer information.
- Result that matters:
- Safe continuation of domestic hot water or space heating via the backup heater until the installer arrives.
- If the emergency selection mode is set to Automatic or acknowledged via the [5.30] pop-up, that confirms the electrical heater will cover heating demand while the heat pump is locked out.
- If emergency takeover is disabled and water temperature falls, that indicates you should inform the installer via [6.2] that the house has no backup heat active.
- Evidence to keep:
- Save a photo of the [5.23] Emergency selection screen and log the time you called the number in [6.2].
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C · Daikin Altherma 4 H F+W+ECH2O operation manual 4PEN773378-1C
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Heat pumps
- Brand
- Daikin
- Product type
- Air-to-water heat pump
Known code variants
- Altherma 4 H F L4-07
- code erreur Daikin Altherma L4-07
- codice L4-07 pompa di calore Daikin
- código L4-07 bomba de calor Daikin
- Daikin Altherma error L4-07
- Daikin Altherma Fehler L4-07
- Daikin heat pump code L4-07
- Daikin L4-07
- Daikin Wärmepumpe Fehlercode L4-07
- défaut L4-07 pompe à chaleur Daikin
- error Daikin Altherma L4-07
- errore Daikin Altherma L4-07
What it means
According to table 14.4.4 in the Daikin Altherma 4 H F installer reference guide (4PEN773391-1C), error code L4-07 belongs to OU: Malfunction of inverter radiating fin temperature rise and is triggered specifically by Overheating of fan 2 radiation fin. The controller stops the heat pump and locks the fault on a manual reset. Whereas L4-06 monitors the fan 1 fin and L4-00/L4-01 monitor the main inverter radiation fin, L4-07 tracks the fan 2 heatsink channel alongside sensor code P4-03. Because airflow blockage or a faulty P4-03 thermistor can mimic overheating, L4-07 by itself never proves that the inverter PCB is broken.
Warnings and stop conditions
- Highsource verified
Never open the outdoor unit switch box yourself. High-voltage capacitors inside the inverter circuit require disconnecting all power for more than 10 minutes and verifying less than 50 V DC before any contact.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C · Daikin Altherma 4 H F+W+ECH2O operation manual 4PEN773378-1C
- Mediumsource verified
Do not bypass thermal protections or cycle external power switches to force L4-07 to clear; Daikin prohibits external switching timers and requires identifying the overheating cause before resetting.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
Symptoms and causes
Probable causes · in order
- Genuine overheating on the fan 2 radiation fin from restricted outdoor heat rejectionCommon
Debris on the outdoor coil, blocked ventilation openings, or high outdoor ambient temperature (up to 43°C in cooling or 40°C in domestic hot water production) raises the fan 2 radiation fin above its thermal cut-out.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C · Daikin Altherma 4 H F+W+ECH2O operation manual 4PEN773378-1C
- Inaccurate fan 2 fin temperature sensor signal associated with P4-03Possible
A degraded thermistor or poor plug contact on the fan 2 fin temperature sensor circuit (which logs automatic code P4-03 when out of range) causes the inverter board to misread fin temperature.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
- Poor heatsink contact or high switch box temperature inside the outdoor unitLess common
Degraded thermal coupling on the fan 2 power stage or an overheated outdoor electrical box (tracked under L3-00) prevents heat dissipation from the fan 2 radiation fin.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
Virtual technician
Does L4-07 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
Daikin Europe N.V. · 2026 · official_doc
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