BoilerFaultCodesVaillant F.65 Fault Code
Also written as F65 — same fault.
The Vaillant F.65 fault code means: your boiler's internal computer is overheating, which has caused the system to shut down to prevent damage to the electronics.. It appears on 68 Vaillant models in our database.
Technical description: PCB processor temperature too high | Check earth connection or electronics defect
What causes the Vaillant F.65 fault?
This fault occurs when the boiler's internal control center exceeds its safe operating temperature and shuts down to prevent the circuit board from melting or catching fire. It is usually caused by an electrical component failing on the board itself or excessive heat building up inside the boiler casing due to poor ventilation. In some cases, external heat source interference or a maturing electronic component can cause this overheating.
This fault is more common during the summer months or during heatwaves, as high ambient temperatures make it harder for the internal electronics to shed heat.
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 F.65: no call-out fees, no surprise bills.
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Vaillant models that show the F.65 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £180-350
- ecoFIT Pure 412 Repair: £180-350
- ecoFIT Pure 418 Repair: £150-300
- ecoFIT Pure 425 Repair: £150-300
- ecoFIT Pure 435 Repair: £150-300
- ecoFIT pure 612
- ecoFIT pure 615
- ecoFIT pure 618
- ecoFIT pure 630
- ecoFIT Pure 825 Repair: £200-450
- ecoFIT Pure 830 Repair: £150-300
- ecoFIT Pure 835 Repair: £150-300
- ecoFIT sustain 415
- ecoFIT sustain 418
- ecoFIT sustain 430
- ecoFIT sustain 615
- ecoFIT sustain 618
- ecoFIT sustain 630
- ecoFIT sustain 825
- ecoFIT sustain 830
- ecoFIT sustain 835
- ecoMAX Repair: £220-450
- ecoMAX 613 Repair: £220-450
- ecoMAX 618 Repair: £220-450
- ecoMAX 622 Repair: £220-450
- ecoMAX 635 Repair: £220-450
- Ecomax Condensing 600/800 series Repair: £300-500
- ecoMAX System 612 Repair: £220-450
- ecoTEC Repair: £280-550
- ecoTEC 65kW Repair: £250-500
- ecoTEC exclusive Repair: £250-£550
- ecoTEC exclusive 627
- ecoTEC plus 412 Repair: £250-500
- ecoTEC plus 415 Repair: £250-500
- ecoTEC plus 418 Repair: £250-500
- ecoTEC plus 424 Repair: £250-500
- ecoTEC plus 430 Repair: £250-500
- ecoTEC Plus 610 Repair: £250-500
- ecoTEC plus 612
- ecoTEC Plus 615 Repair: £250-450
- ecoTEC plus 618
- ecoTEC Plus 620 Repair: £250-450
- ecoTEC plus 624
- ecoTEC Plus 625 Repair: £250-450
- ecoTEC Plus 630 Repair: £250-450
- ecoTEC Plus 635 Repair: £250-450
- ecoTEC plus 637 Repair: £180-450
- ecoTEC Plus 826 Repair: £250-450
- ecoTEC Plus 832 Repair: £250-450
- ecoTEC Plus 840 Repair: £250-450
- ecoTEC Plus 938 Repair: £250-450
- ecoTEC plus aquaPLUS Repair: £250-450
- ecoTEC Pro Repair: £250-450
- ecoTEC Pro / ecoTEC Plus Repair: £180-450
- ecoTEC Pro 24 Repair: £250-450
- ecoTEC Pro 28 Repair: £250-450
- ecoTEC Pro 30 Repair: £250-450
- ecoTEC sustain Repair: £250-450
- Home Combi Repair: £150-350
- Home System Repair: £250-450
- Thermocompact Repair: £250-£450
- Turbomax 824/828 Repair: £250-450
- Turbomax Plus Repair: £250-450
- Turbomax Plus 824/828E Repair: £180-350
- Turbomax Plus 828 Repair: £280-450
- Turbomax Plus 828 E Repair: £180-350
- Turbomax Plus VUW 242E Repair: £180-350
- Turbomax Plus VUW 242EH Repair: £180-350
Source
Vaillant F.65 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 425 manual (PDF)
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant ecoFIT pure 630 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026