- Heat pumps
- Air-to-water heat pump
L1-55
Daikin Altherma 4 H F L1-55: Malfunction of INV PCB
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
L1-55 means “Malfunction of INV PCB” on the scoped Altherma 4 H F family. Daikin records this trigger: Malfunction of INV PCB: fan driver error. Effect: Heat pump will stop operating. The table marks the reset as power cycle.
Safety first
Stop and check this first
- Stop and isolate the installation for smoke, burning smell, sparks, unusual heat, water near electrical parts, suspected refrigerant release or repeated protective trips. Do not open the R290 refrigerant circuit or live electrical compartments.
Safe checks you can perform
- Preserve the diagnostic state
- Let the automatic reset logic decide
- Keep the check outside the casing
Leave these tasks to a qualified professional
- Do not attempt this professional task: Measured handoff for L1-55
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.
Measured handoff for L1-55
What they doGive the technician L1-55, both model numbers, the source trigger “Malfunction of INV PCB: fan driver error”, the effect “Heat pump will stop operating”, reset result and recurrence conditions. They should follow Daikin's exact controller decision branch and compare live measurements with the service values before replacing parts.
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.
Preserve the diagnostic state
Photograph L1-55 and the complete display. Record both unit model numbers, operating mode, requested temperatures, weather, system pressure shown to the user and the moment the code appeared.
Stop and isolate the installation for smoke, burning smell, sparks, unusual heat, water near electrical parts, suspected refrigerant release or repeated protective trips. Do not open the R290 refrigerant circuit or live electrical compartments.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
Let the automatic reset logic decide
Daikin marks this code as automatic reset. Do not cycle breakers or force repeated acknowledgements. Record whether the controller clears it and the exact operating state in which it returns.
Stop and isolate the installation for smoke, burning smell, sparks, unusual heat, water near electrical parts, suspected refrigerant release or repeated protective trips. Do not open the R290 refrigerant circuit or live electrical compartments.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
Keep the check outside the casing
Use only normal controls and user-accessible observations. Do not remove covers, bypass a safety device or replace a part from the code alone.
Stop and isolate the installation for smoke, burning smell, sparks, unusual heat, water near electrical parts, suspected refrigerant release or repeated protective trips. Do not open the R290 refrigerant circuit or live electrical compartments.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
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 L1-55
- code erreur Daikin Altherma L1-55
- codice L1-55 pompa di calore Daikin
- código L1-55 bomba de calor Daikin
- Daikin Altherma error L1-55
- Daikin Altherma Fehler L1-55
- Daikin heat pump code L1-55
- Daikin L1-55
- Daikin Wärmepumpe Fehlercode L1-55
- défaut L1-55 pompe à chaleur Daikin
- error Daikin Altherma L1-55
- errore Daikin Altherma L1-55
What it means
In guide 4P773391-1C (2026.02), Daikin assigns L1-55 to “Malfunction of INV PCB”. The documented trigger is “Malfunction of INV PCB: fan driver error” and the operating effect is “Heat pump will stop operating”. This is a precise controller decision for Daikin Altherma 4 H F — EPSK(S)04~14A + EPVX07~14S18+23A; it does not by itself prove which component failed.
Warnings and stop conditions
- Highsource verified
Stop and isolate the installation for smoke, burning smell, sparks, unusual heat, water near electrical parts, suspected refrigerant release or repeated protective trips. Do not open the R290 refrigerant circuit or live electrical compartments.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
Symptoms and causes
Probable causes · in order
- What the controller establishedConfirmed
Daikin's table defines the condition as “Malfunction of INV PCB” and gives this exact trigger: Malfunction of INV PCB: fan driver error.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
- What the unit does nextConfirmed
Documented effect: Heat pump will stop operating. Reset classification: Power cycle. A cleared display is not proof of repair.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
Virtual technician
Does L1-55 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
Was this entry useful?