Atlantic W01

Atlantic error code W01 indicates: Atlantic Alféa Excellia / Extensa A.I. / Alféa Hybrid Duo Inverter Heat Pump: Diagnostic fault code W01 registered by the microcomputer controller. Outdoor evaporator coil heavy frost warning indicator.

The primary root cause for Atlantic code W01 is: On Atlantic appliances engineered with co-developed Fujitsu twin-rotary DC inverter outdoor stage, Siemens Navistem / RVS hydraulic regulator, electronic expansion valve with 46 Ω stepper phases, and 10 kΩ NTC flow/return temperature sensors: excessive outdoor coil frost accumulation detected by evaporating temperature persisting below -5°C for > 45 minutes Metrological tolerance verification: defrost thermistor reading < -5.0°C; 4-way valve initiates reverse cycle..

To resolve error code W01: Disconnect mains power before servicing. Unplug the harness at the main PCB and use a calibrated digital multimeter: test outdoor coil defrost thermistor calibration and check bottom base pan trace heater resistance (~180 Ω). Inspect contacts for pin oxidation or loose terminals. Replace defective part if out of tolerance, re-energize and clear error: On the Navistem user controller: press OK and hold the 'i' button for 3 seconds to access Specialist mode. Go to line 6700-6800 (Diagnostics), select 'Reset fault log' and set to 'Yes', then press OK. For hard lockout, switch off the 230V/400V mains breaker for 60 seconds to discharge the DC link.

Resetting power (unplugging for 5–10 minutes) clears temporary memory errors. However, if Atlantic code W01 persists, the physical component causing On Atlantic appliances engineered with co-developed Fujitsu twin-rotary DC inverter outdoor stage, Siemens Navistem / RVS hydraulic regulator, electronic expansion valve with 46 Ω stepper phases, and 10 kΩ NTC flow/return temperature sensors: excessive outdoor coil frost accumulation detected by evaporating temperature persisting below -5°C for > 45 minutes Metrological tolerance verification: defrost thermistor reading < -5.0°C; 4-way valve initiates reverse cycle. must be inspected or replaced.

Set a digital multimeter to ohms (Ω). Disconnect power and test NTC Temperature Sensor Probe (Thermistor) across Across sensor pins 1-2 (unplugged harness). Expected nominal reading is 4.8kΩ–12kΩ (at 20°C–25°C). Tolerance: Negative temperature coefficient: resistance drops smoothly when warmed with fingers. OL = open circuit..

Standard electrical safety protocol: 1. Disconnect 230V mains power before opening panels. 2. Verify zero voltage at test points. 3. Allow hot water or heating elements to cool below 30°C before handling.