Vaillant fault code F.788
Fault code F.788 on a Vaillant heat pump (including Hydraulisch station and aroTHERM split) means: The electronics of the high-efficiency pump have detected a fault (e.g. dry running, blockage, overvoltage, undervoltage) and have switched off with lockout. 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.788 on a Vaillant heat pump indicates: The electronics of the high-efficiency pump have detected a fault (e.g. dry running, blockage, overvoltage, undervoltage) and have switched off with lockout.
Applies to
Vaillant Hydraulisch station, aroTHERM split, aroTHERM split uniTOWER, flexoCOMPACT exclusive, uniTOWER pure, VWF 118/4, VWF 88/4, VWL 107 7.2 IS S1 _ VWL 105 7.2 AS 230V S3, VWL 107 7.2 IS S1 _ VWL 45 7.2 AS 230V S3, VWL 107 7.2 IS S1 _ VWL 65 7.2 AS 230V S3, VWL 107 7.2 IS S1 _ VWL 85 7.2 AS 230V S3, VWL 107 7.2 IS _ VWL 105 7.2 AS 230V S3, VWL 107 7.2 IS _ VWL 45 7.2 AS 230V S3, flexoTHERM, VWF 117/4, VWF 157/4, VWF 197/4, VWF 57 /4, VWF 87/4.
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.
This message does not point directly to one faulty part. These are the parts that most often fit this appliance:
- Vaillant temperature sensor € 31.36
- Vaillant sealing ring set of 3 pcs € 13.07
- Vaillant sensor for e.g. aroTHERM Pro VWL 75/7.1 A 230V 0020269357 € 20.26
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.788 mean?
The electronics of the high-efficiency pump have detected a fault (e.g. dry running, blockage, overvoltage, undervoltage) and have switched off with lockout.
How do I fix fault code F.788 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.788?
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.788 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 →