Heat pump fault codes

Vaillant heat pump faults: fault codes, causes and parts (page 2 of 2)

Codes 151 to 227 of the 227 fault codes for Vaillant. Looking for a specific code? Use the search on the first page.

Vaillant heat pump fault codes 151 to 227 of 227

The code list is split over 2 pages. Looking for a specific code? Use the search on the first page: it searches all 227 codes in one go.

Code	Cause
F.740	Inlet temperature in the ambient circuit too low for compressor start in heating mode: Air/brine: ambient circuit inlet temperature < -28 °C, ground/brine: ambient circuit inlet temperature < −7°C, groundwater/brine: groundwater inlet temperature < 2 °C
F.740	Inlet temperature in the ambient circuit too low for compressor start - Heating: VWL air inlet temperature < 0 °C - VWS ambient circuit inlet temperature < -10 °C, Cooling: VWL air inlet temperature < 15 °C
F.740	Inlet temperature in the ambient circuit too low for compressor start in heating mode: Air/brine: ambient circuit inlet temperature < -28 °C, ground/brine: ambient circuit inlet temperature < -7 °C, groundwater/brine: groundwater inlet temperature < 2 °C
F.741	Return temperature in the emitter circuit too low for compressor start, Heating: return temperature < 5 °C, Cooling: return temperature < 10 °C
F.741	Return temperature in the emitter circuit too low for compressor start, Heating: return temperature < 5 °C, Cooling: return temperature < 10 °C
F.741	During defrosting the return temperature drops below 13 °C
F.741	Return temperature in the emitter circuit too low for compressor start - Heating: return temperature < 5 °C, Cooling: return temperature < 7 °C
F.742	Inlet temperature in the ambient circuit too high for compressor start, brine inlet temperature > 50 °C, supply of external heat into the ambient circuit
F.742	Inlet temperature in the ambient circuit too high for compressor start - Heating: air inlet temp. > 25 °C, Cooling: air inlet temp. > 37 °C
F.742	Inlet temperature in the ambient circuit too high for compressor start, brine inlet temperature > 50 °C, supply of external heat into the ambient circuit
F.743	Return temperature in the emitter circuit too high for compressor start, Heating: return temperature > 55 °C to 60 °C (depending on the brine inlet temperature), Cooling: return temperature > 35 °C
F.743	Return temperature in the emitter circuit too high for compressor start, Heating: return temperature > 55°C to 60 °C (depending on the brine inlet temperature), Cooling: return temperature > 35 °C
F.750	Cable insulation defective, connection interrupted
F.751	Supply voltage of the product is too low, finned heat exchanger or heat exchanger is fouled
F.752	The parameter ""Max. duration of the power interruption"" is set incorrectly (see ""Heat pump setting parameters"" in the appendix), inverter box damaged, inverter box cooler is blocked, incorrect supply voltage
F.752	Internal electronics fault on the inverter PCB, mains voltage outside 70V – 282V
F.752	Internal electronics fault on the inverter PCB, mains voltage outside 70 V – 282 V
F.752	Internal electronics fault on the inverter PCB. Mains voltage outside 70 V – 282 V.
F.753	No communication between the inverter and the thermostat PCB of the outdoor unit.
F.753	No communication between the inverter and the thermostat PCB of the outdoor unit
F.753	The parameter ""Max. duration of the power interruption"" is set incorrectly (see ""Heat pump setting parameters"" in the appendix), connection between the main PCB and the inverter box is damaged or open circuit, inverter box is not switched on
F.754	Connection between the main PCB and the fan PCB is damaged or open circuit, fan PCB is defective
F.755	Mechanical or electrical problem. Move the four-way valve from the thermostat. During the movement, check that the coil voltage is correct.
F.755	Wrong position of the four-way valve. If, in heating mode, the flow temperature is lower than the return temperature in the emitter circuit, temperature sensor in the EEV ambient circuit shows incorrect temperature
F.755	Wrong position of the four-way valve. If, in heating mode, the flow temperature is lower than the return temperature in the emitter circuit, temperature sensor in the EEV ambient circuit shows incorrect temperature.
F.755	Wrong position of the four-way valve. If, in heating mode, the flow temperature is lower than the return temperature in the emitter circuit. Temperature sensor in the EEV ambient circuit shows incorrect temperature.
F.757	The compressor has stopped several times before the minimum run time was reached. The product is therefore locked out. In a system without a buffer and with a low heating water volume, the temperature can rise or fall very quickly when the compressor starts. Depending on the starting conditions, there is then a risk that the product will stop.
F.758	Short circuit in the compressor cable, cable connection on compressor not screwed tight
F.759	Frequency inverter: signal from the internal sensor (current, temperature, detection circuit) invalid
F.761	Phase sequence at compressor incorrect, cable connection on compressor not screwed tight, compressor defective
F.762	Voltage at the DC intermediate circuit supply too low, voltage at the DC intermediate circuit supply too high, cable connection on compressor not screwed tight, mains voltage invalid
F.774	Sensor not connected or sensor input short-circuited.
F.774	Sensor not connected or sensor input short-circuited
F.774	The temperature sensor is defective or not correctly connected to the main PCB.
F.782	No electrical connection No eBUS connection
F.783	Cable not connected or incorrectly connected
F.784	Cable not connected or incorrectly connected
F.785	Confirmation signal missing, the fan is rotating.
F.785	Confirmation signal that the fan is rotating is missing
F.786	The safety temperature limiter of the defroster has opened due to flow rate too low or brine temperatures above 65 °C, use of the defroster outside the permitted range, electric defrosting with brine circuit not filled, electric defrosting with brine temperatures above 115 °C causes the thermal fuse of the safety temperature limiter to blow and requires replacement.
F.787	Pressure loss in the ambient circuit due to leak or air pocket, emitter circuit pressure switch defective
F.787	Pressure loss in the ambient circuit due to leak or air pocket, emitter circuit pressure switch defective, wire either between X110B and X110 or between X110 and X110A of the mains connection PCB not connected. No 230 V present at X131. Interpreted as opening of the input contact, jumper at X131 (delivery condition). Larger voltage fluctuations in the power supply can cause the error message, fuse T4 defective
F.788	The electronics of the high-efficiency pump have detected a fault (e.g. dry running, blockage, overvoltage, undervoltage) and have switched off with lockout.
F.788	The electronics of the high-efficiency pump have detected a fault (e.g. dry running, blockage, overvoltage, undervoltage) and have switched off with lockout.
F.789	Sensor not connected or sensor input short-circuited
F.790	Sensor not connected or sensor input short-circuited
F.792	Sensor not connected or sensor input short-circuited
F.792	Sensor not connected or sensor input short-circuited
F.792	Temperature sensor not connected or sensor input short-circuited.
F.793	Temperature sensor not connected or sensor input short-circuited.
F.793	Sensor not connected or sensor input short-circuited
F.793	Sensor not connected or sensor input short-circuited
F.797	Sensor not connected or sensor input short-circuited
F.797	Sensor not connected or sensor input short-circuited
F.798	Sensor not connected or sensor input short-circuited
F.798	Sensor not connected or sensor input short-circuited
F.799	Sensor not connected or sensor input short-circuited
F.799	Sensor not connected or sensor input short-circuited
F.817	Fault in the compressor (e.g. short circuit), fault in the inverter, compressor connection cable defective or loose
F.817	Fault in the compressor (e.g. short circuit), fault in the inverter, compressor connection cable defective or loose.
F.818	Wrong mains voltage for operation of the inverter, switch-off by the energy supplier
F.818	Wrong mains voltage for operation of the inverter. Switch-off by the energy supplier
F.819	Internal overheating of the inverter.
F.819	Internal overheating of the inverter
F.820	Pump sends no signal back to the heat pump
F.820	Pump sends no signal back to the heat pump.
F.821	Sensor not connected or sensor input short-circuited. Both flow temperature sensors in the heat pump are defective.
F.821	Sensor not connected or sensor input short-circuited, both flow temperature sensors in the heat pump are defective
F.823	The hot gas thermostat switches off the heat pump if the pressure in the refrigerant circuit is too high. After a waiting time, a further start attempt of the heat pump follows. After three consecutive failed start attempts, an error message is displayed, refrigerant circuit temperature max.: 110 °C, waiting time: 5 min (after the first occurrence), waiting time: 30 min. (after the second and each subsequent occurrence), fault counter is reset when both conditions occur: heat demand without premature switch-off, 60 min undisturbed operation
F.823	The hot gas thermostat switches off the heat pump if the pressure in the refrigerant circuit is too high. After a waiting time, a further start attempt of the heat pump follows. After three consecutive failed start attempts, an error message is displayed: refrigerant circuit temperature max.: 130 °C, waiting time: 5 min (after the first occurrence), waiting time: 30 min. (after the second and each subsequent occurrence), fault counter is reset when both conditions occur: heat demand without premature switch-off, 60 min undisturbed operation
F.824	Pressure loss in the emitter circuit due to leak or air pocket, emitter circuit pressure sensor defective
F.825	Refrigerant circuit temperature sensor (vapour) not connected or sensor input short-circuited
F.827	Sensor not connected or sensor input short-circuited
F.842	DIP switch setting does not match hardware, outdoor unit defective
F.905	Communication with CIM module has been interrupted
F.9998	Cable not connected or incorrectly connected. Outdoor unit without supply voltage.
F.9998	eBUS cable not connected or incorrectly connected, outdoor unit without supply voltage

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