Vaillant fault code F.103
Fault code F.103 on a Vaillant heat pump (including Hydraulisch station) means: Wrong thermostat PCB installed on the outdoor unit. Reset the appliance once. If the code comes back, a part is usually faulty. 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.103 on a Vaillant heat pump indicates: Wrong thermostat PCB installed on the outdoor unit.
Applies to
Vaillant 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.
Fault code F.103 on other Vaillant series
The same code does not mean the same thing on every series. Check the rating plate to see which series you have:
- F.103 on aroTHERM Monoblock, VWL 115/2 A 400 V, VWL 155/2 A 400V, VWL 55/2 A 230V, VWL 55/3 A 230 V, VWL 85/2 A 230 V: Parameter ""Max. duration of the circuit breaker"" is set incorrectly (see ""Heat pump setting parameters"" in the appendix), the main PCB or inverter installed as a spare part does not match the product.
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.
For fault code F.103, the part involved is usually in the category: PCB.
This message does not point directly to one faulty part. If the code keeps coming back, view the Vaillant parts:
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.103 mean?
Wrong thermostat PCB installed on the outdoor unit.
How do I fix fault code F.103 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.103?
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.103 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 →