Vaillant Boiler Fault Codes – Witney & Surrounding Areas

Last updated: February 2026

If your Vaillant boiler is showing a fault code (typically displayed as an “F” code), this comprehensive guide explains what the code means, what may have caused it, and what steps you should take next.

We diagnose, service and repair Vaillant domestic and commercial boilers across Witney and the wider Oxfordshire area — including ecoTEC exclusive, ecoTEC plus, ecoTEC pro, ecoFIT pure, older legacy Vaillant models and larger commercial plant-room systems.

Important: Fault codes can vary slightly depending on model generation and software version. If your boiler repeatedly locks out or you are unsure of the cause, contact us directly and we will diagnose the issue safely and correctly.

Understanding Vaillant Fault Codes

Vaillant boilers constantly monitor system pressure, temperature sensors, combustion performance, fan speed, gas valve operation, pump movement and electronic communication. When a parameter moves outside safe operating limits, the boiler will shut down and display a fault code.

Many codes relate to pressure, ignition, flame detection, sensors or electronic communication. Some can be simple to resolve, while others require a qualified Gas Safe engineer.

Full Vaillant Fault Code Directory

Fault Code	Typical Meaning
F22	Low water pressure
F23	Flow/return temperature difference too high
F24	Water circulation fault
F27	Flame detection issue
F28	Ignition failure
F29	Flame failure during operation
F32	Fan speed fault
F49	eBUS communication fault
F61	Gas valve control fault
F62	Gas valve delay fault
F64	Electronics error
F65	Electronics overheating
F67	Flame signal incorrect
F70	Appliance ID fault
F71	Flow temperature sensor fault
F72	Flow/return sensor mismatch
F73	Water pressure sensor fault
F74	Water pressure sensor wiring fault
F75	Pump not detecting pressure rise
F76	Primary heat exchanger overheating
F77	Condensate pump fault (where fitted)
F83	Incorrect temperature change detection
F84	Flow/return sensor inconsistency
F85	Flow/return sensor swapped

What Should You Do If Your Boiler Shows a Fault?

1. Check the system pressure

Pressure should typically sit between 1.0 and 1.5 bar when cold.

2. Check gas supply

Ensure other gas appliances are working.

3. Reset once only

If the fault returns immediately, further investigation is required.

4. Contact us

If the boiler repeatedly locks out, our Gas Safe registered engineers can diagnose and repair the issue safely.

Vaillant Boiler Guarantees

Vaillant boilers are supplied with manufacturer guarantees (not warranties). The guarantee period depends on the boiler range, installer accreditation level and whether the appliance was registered correctly.

Boiler Range	Standard Guarantee	Registered by myREWARDS Installer	With Vaillant Filter + myREWARDS
ecoTEC exclusive (Green iQ)	5 years	Up to 8 years*	10 years
ecoTEC plus	5 years	Up to 8 years*	10 years
ecoTEC pro	2 years	7 years	7 years
ecoFIT pure	2 years	7 years	10 years

*Extended guarantees depend on installer accreditation level and correct product registration.

Domestic & Commercial Vaillant Repairs in Witney

We repair and service Vaillant combi, system and regular boilers as well as commercial Vaillant cascade and plant-room systems throughout Witney and surrounding Oxfordshire areas.

If your Vaillant boiler is displaying a fault code, contact us directly for fast diagnosis and professional repair.

Need a Vaillant Boiler Repair in Witney?

If your Vaillant boiler is showing a fault code, repeatedly locking out, losing pressure or failing to ignite, our Gas Safe registered engineers can diagnose and repair the issue quickly and safely. We cover both domestic and commercial Vaillant systems throughout Witney and the surrounding Oxfordshire areas.