BoilerFaultCodesVaillant Connection Fault Code
Also written as CONNECTION — same fault.
The Vaillant Connection fault code means: your boiler's main internal computer and the front control panel have lost their connection, meaning the unit cannot receive instructions or show you what is happening.. It appears on 12 Vaillant models in our database.
Technical description: NocommunicationbetweenthePCB andtheuserinterface | Electronicsdefective
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Vaillant models that show the Connection fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £180-450
- Combi Compact 242EB Repair: £180-450
- Combi Compact 282EB Repair: £180-450
- ecoFIT pure Repair: £150-300
- ecoFIT Pure 418 Repair: £150-300
- ecoFIT Pure 425 Repair: £150-300
- ecoFIT Pure 435 Repair: £150-300
- ecoFIT Pure 825 Repair: £150-300
- ecoFIT Pure 830 Repair: £180-350
- ecoFIT Pure 835 Repair: £150-300
- ecoTEC Plus 610 Repair: £200-450
- ecoTEC plus Regular Repair: £250-450
Source
Vaillant Connection fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026