Vaillant fault code F.842
Fault code F.842 on a Vaillant heat pump (including uniTOWER pure) means: DIP switch setting does not match hardware, outdoor unit defective. 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.842 on a Vaillant heat pump indicates: DIP switch setting does not match hardware, outdoor unit defective.
Applies to
Vaillant uniTOWER pure, 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, VWL 107 7.2 IS _ VWL 65 7.2 AS 230V S3, VWL 107 7.2 IS _ VWL 85 7.2 AS 230V S3.
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 filter l120mm w39,83mm h190mm € 11.11
- 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.842 mean?
DIP switch setting does not match hardware, outdoor unit defective.
How do I fix fault code F.842 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.842?
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.842 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 →