Vaillant fault code F.703
Fault code F.703 on a Vaillant heat pump (including flexoCOMPACT exclusive and geoTHERM 3 kW) means: Sensor not connected or sensor input short-circuited. Reset the appliance once. If the code comes back, a part is usually faulty, often a temperature sensor. You can check the water pressure and settings yourself; leave work on gas-carrying parts to a certified gas engineer.
After a safety alert (gas, flue gas, combustion), reset no more than once and call in a certified gas engineer. If you smell gas, call your national gas emergency number or 112 immediately.
Cause
Fault code F.703 on a Vaillant heat pump indicates: Sensor not connected or sensor input short-circuited.
Applies to
Vaillant flexoCOMPACT exclusive, geoTHERM 3 kW, VWF 118/4, VWS 36/4.1 230V, flexoTHERM, VWF 117/4, VWF 157/4, VWF 197/4, VWF 57 /4, VWF 87/4, Hydraulisch station, VWZ MEH 97/6 w _ VWL 35_6 A 230V, VWZ MEH 97_6 w _ VWL 105_6 A, VWZ MEH 97_6 w _ VWL 125_6 A, VWZ MEH 97_6 w _ VWL 55_6 A 230V, VWZ MEH 97_6 w _ VWL 65_6 A 230V, VWZ MEH 97_6 w _ VWL 75_6 A 230V.
Matching parts
Vaillant parts are available from Instalpunt; shipping to EU countries from €17.95 (€24.95 for more distant countries), usually 3–5 working days.
Parts by Vaillant series: ecoTEC plus · ecoTEC pro.
Based on the cause, these original Vaillant parts fit (always check the type number of your appliance):
- Vaillant pressure sensor VHR18-22/3C24-28/3C VHR CW3 4/3 for ecoTEC plus and ecoTEC pro etc. € 24.18
- Vaillant temperature sensor € 31.36
- Vaillant brine sensor with wiring harness € 45.74
Further reading on this cause
Other Vaillant codes with the same cause
- F.022 — Water pressure sensor defective, open circuit in the wiring harness, solenoid valve of…
- F.042 — Sensor not connected or sensor input short-circuited
- F.073 — Wire to the water pressure sensor is open circuit or has a short circuit
- F.086 — Contact S20 on the heat pump main PCB (HMU) open, incorrect setting of the maximum…
- F.094 — Flow rate sensor not connected or sensor input short-circuited
- F.1288 — Sensor defective or not correctly connected to the VWZ AI heat pump control module.
Fix it yourself or call an engineer?
Always consult the manual for your appliance and work safely. If in doubt or if the fault comes back, call in a qualified professional. A question about a part? Write to us at info@instalpunt.nl.
Frequently asked questions
What does Vaillant heat pump fault code F.703 mean?
Sensor not connected or sensor input short-circuited.
How do I fix fault code F.703 on a Vaillant heat pump?
First check the cause described above. Then restart the appliance using the reset button. If the message comes back, a part usually needs replacing or the fault needs to be repaired by a qualified professional.
Which parts do I need for Vaillant fault code F.703?
That depends on the exact cause. In the Vaillant parts overview at Instalpunt you will find the current price and stock for each part.
Can I fix fault code F.703 myself?
You can reset the appliance and check things like the water pressure or settings yourself. Work on gas-carrying parts must be left to a certified gas engineer.
All Vaillant heat pump faults and codes at a glance →