BoilerFaultCodesVaillant D.47 Fault Code
Also written as D47 — same fault.
The Vaillant D.47 fault code means: your boiler's outside temperature sensor is either giving an incorrect reading or has lost communication with the main control system.. It appears on 28 Vaillant models in our database.
Technical description: Outside temperature with weather compensator – Vaillant controller only
What causes the Vaillant D.47 fault?
This fault occurs when the boiler loses contact with the sensor located on the outside of your property, which is responsible for monitoring the outdoor temperature. The most common reasons are a break in the communication cable due to weather damage or a internal component failure within the sensor itself. Without this data, the boiler cannot automatically adjust its efficiency based on the weather conditions outside.
This fault is often noticed during the transition into autumn or winter when the heating system's weather compensation features are first called upon after the summer break.
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 →Avoid the next call-out bill
A cover plan would handle faults like D.47: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Vaillant models that show the D.47 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £90-180
- ecoFIT Pure 418 Repair: £90-180
- ecoFIT Pure 425 Repair: £90-180
- ecoFIT Pure 435 Repair: £90-180
- ecoFIT Pure 825
- ecoFIT Pure 830 Repair: £120-200
- ecoFIT Pure 835 Repair: £90-180
- ecoMAX Repair: £120-200
- ecoMAX 613 Repair: £100-200
- ecoMAX 618 Repair: £120-200
- ecoMAX 622 Repair: £120-200
- ecoMAX 635 Repair: £120-200
- ecoMAX 824E Repair: £100-200
- ecoMAX 828E Repair: £120-200
- Ecomax Condensing 600/800 series Repair: £100-200
- ecoMAX System 612 Repair: £120-220
- ecoTEC Repair: £100-220
- ecoTEC 65kW Repair: £100-200
- ecoTEC Plus 615
- ecoTEC Plus 620
- ecoTEC Plus 625
- ecoTEC Plus 630
- ecoTEC Plus 635
- ecoTEC Plus 840
- ecoTEC Pro / ecoTEC Plus
- ecoTEC sustain
- Home Combi Repair: £120-200
- Home System
Source
Vaillant D.47 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant ecoMAX manual (PDF)
- Vaillant ecoMAX System 612 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026