Common Vaillant Boiler Fault Codes

Vaillant boilers are renowned for their efficiency and reliability, but like any heating system, they can occasionally encounter issues. When something goes wrong, your boiler will usually display a fault code, a built-in indicator that tells you what's causing the issue. While some codes can indicate minor problems that you can fix yourself, others signal the need for professional attention.

Understanding these codes can save you time, stress, and even money. Whether it's a pressure issue or an ignition failure, knowing what your boiler is trying to tell you helps you respond correctly and quickly.

At Maintracts Services, we've been serving London since 1974, providing expert plumbing, heating, electrical, and drainage solutions for over 50 years. Our qualified team is trusted by homeowners and landlords alike, especially when it comes to complex boiler diagnostics and repairs. Whether your Vaillant boiler requires a quick fix or a full service, we're ready to help.

If you're seeing a fault code and need urgent support, call us on 020 8682 2244 or contact us. We're available 24/7 to help.

 

 

What Are Vaillant Boiler Fault Codes?

Vaillant boiler fault codes are alphanumeric indicators (such as F22, F28, or F75) that appear on your boiler's display when an issue occurs. Each code corresponds to a specific fault. For example, F22 signals low water pressure, F28 indicates an ignition failure, and F75 indicates an issue with the pump or pressure sensor. 

These codes are built-in diagnostic tools designed to help quickly pinpoint the problem. While some faults can be easily checked or topped up at home, others call for expert repair. Understanding what they mean is the first step to getting your heating back on track safely and efficiently.  

Also Read: Ariston Boiler Error Codes       

 

Common Vaillant Boiler Fault Codes And How To Fix Them

Understanding fault codes on your Vaillant boiler can help you troubleshoot minor issues and know when to call a professional. These codes appear on your boiler display when there's a problem, ranging from sensor faults to ignition failures. While some can be resolved with a simple reset, others require urgent attention from qualified engineers. Below are some of the most common Vaillant error codes, their causes, and suggestions on what you can try before calling an engineer.

1. Temperature Sensor And NTC Faults

These codes relate to NTC (Negative Temperature Coefficient) thermistors, which help regulate the temperature of boilers. When they fail, the system may shut down to prevent overheating.

Codes: F.00 / F.01 / F.10 / F.11 / F.13

• What it means: The flow or return temperature sensor is damaged, has a short circuit, or is disconnected. 
• Common causes: Faulty or disconnected sensors, wiring issues. 
• What to try: Turn off the boiler, wait a minute, then reset. If the code returns, contact an engineer to inspect and replace the sensor. 

Code: F.20

• What it means: Boiler over-temperature protection has been activated. 
• Common causes: Blockages, pump failure, trapped air, or poor water circulation. 
• What to try: Let the boiler cool down fully before resetting. If it trips again, the system may need to be flushed or the pump checked. 

Codes: F.22 / F.24

• What it means: Low water pressure, dry fire or pump fault. 
• Common causes: Airlocks, leaks, insufficient pressure, pump failure. 
• What to try: Use the filling loop to top up pressure to 1.0–1.5 bar. If pressure drops again, check for leaks or contact a professional engineer for assistance. 

2. Ignition And Flame Detection Errors

These codes suggest a problem with the boiler igniting or maintaining a flame.

Codes: F.28 / F.29

• What it means: Ignition failure or flame lost during operation. 
• Common causes: Frozen condensate pipe, gas supply issues, faulty electrodes or flue blockages. 
• What to try: 

• • Check if other gas appliances work. 
  • If safe, reset the boiler once. 
  • In winter, thaw the condensate pipe with warm water.
    Persistent issues need a gas-safe engineer to inspect ignition parts. 

Codes: F.27 / F.67

• What it means: Flame detection error or simulation fault. 
• Common causes: Defective detection probe, PCB fault. 
• What to try: Reset once. If the fault reoccurs, the PCB or detection probe may need to be replaced. 

3. Gas Valve And Control Unit Errors

These indicate faults with the gas supply control or the internal electronics.

Codes: F.60 / F.61 / F.62

• What it means: Faults within the gas valve control system. 
• Common causes: Short circuits, faulty gas valves, or wiring issues. 
• What to try: Do not attempt to fix yourself. Turn off the boiler and contact a qualified engineer for assistance. 

Codes: F.63 / F.64 / F .65

• What it means: Electronic control system errors, including EEPROM failure. 
• Common causes: Internal boiler faults or sensor malfunction. 
• What to try: These faults require diagnostic tools. Book a professional inspection. 

4. Pressure And Pump Related Issues

These codes appear when the water pressure is too low, or the pump isn't functioning as it should.

Code: F.75

• What it means: No pressure change is detected when a pump starts. 
• Common causes: Faulty pressure sensor or airlock. 
• What to try: 
• Check the pressure gauge. 
• Top up to 1.2–1.5 bar using the filling loop. 
• Bleed radiators if air is present in the system. 

Codes: F.73 / F.74  

• What it means: Pressure sensor reading out of expected range. 
• Common causes: Sensor failure or blockage. 
• What to try: If the pressure gauge appears normal but the code persists, the sensor may need to be replaced. 

5. Fan, Flue, And Airflow Problems

These are safety-related codes indicating ventilation or combustion issues. 

Codes: F.32 / F.33

• What it means: Fan speed error or fan not detected. 
• Common causes: Fan motor fault, PCB issue. 
• What to try: These are not DIY fixes. Turn off the boiler and book a gas-safe engineer. 

Codes: F.36 / F.37 

• What it means: Flue gas or air pressure switch fault. 
• Common causes: Blocked flue, broken pressure switch. 
• What to try: Check for external blockages (e.g. snow or debris in the flue). If clear, call an engineer to inspect the internal components.  

Pro Tip: If your Vaillant code isn't listed here, scroll down for our complete table of codes by boiler model and series. 

Also Read: Baxi Boiler Error Codes    

 

Vaillant Boiler Fault Codes By Model

Not all Vaillant models use the same fault codes. Below is a breakdown of the most common codes grouped by boiler model to help you identify issues more quickly.

1. Ecotec Plus / Ecotec Pro (Combi & System Models)

These models often display a combination of F, S, D, and P codes. 

• F22 – Low water pressure 
• F28 – Ignition failure 
• F29 – Flame lost after ignition 
• F75 – Pressure sensor issue 
• S.53 – Temperature rise too steep 
• D.00 – No heating demand 
• P.01 – Burner active, pump not running 

Note: These models are commonly used in homes throughout London. Most issues can be resolved by topping up the pressure or resetting it once. 

2. Turbomax Plus 824 / 828E

Older combi boilers with simpler diagnostic displays. 

• F20 – Overheating 
• F28 – Ignition failure 
• F29 – Flame extinguished 
• F24 – Pump failure 
• F22 – Dry fire (low water pressure) 

A reminder: Due to age, recurring faults on Turbomax models often require replacement parts or full servicing.

3. EcoMax Pro 18 / 28E

Reliable system boilers with sensitive voltage and temperature monitoring. 

• F19 – Mains voltage too low 
• F23 – Flow and return temperatures too far apart 
• F11 – Flow temperature sensor fault 
• F13 – Return temperature sensor fault 

Optional advice: Check your power socket if F19 appears. Avoid using extension leads with boilers.

4. EcoTEC 65kW | EcoMax Pro 828E | Regular Gas Boilers

These are often larger or commercial-type installations.  

• F00–F10 – General temperature sensor faults 
• F22 – System pressure too low 
• F83 – Flow and return temperatures too far apart 
• F84 – Calibration error or issue with a temperature gradient 

Callout tip: Larger Vaillant boilers are more sensitive to airlocks and pressure imbalances. Annual servicing is key. 

Also Read: Ideal Logic Boiler Fault Codes      

 

Complete Vaillant Error Code Table

Here's a quick reference table of the most common Vaillant boiler codes: 

Code	Meaning	Recommended Action
F22	Low water pressure	Top up via filling loop
F28	Ignition failed	Check the gas supply, reset it once, and call the engineer if it repeats
F75	No pressure sensor response	Reset; sensor or pump may need replacing
F29	Flame lost after ignition	Check the condensate pipe, reset it, and call the engineer
F20	Boiler overheating	Bleed radiators; engineer inspection advised
S.53	Temperature rises too fast	Bleed radiators; power flush may help
D.00	No heating demand	Check thermostat or smart controls
F83	Temperature imbalance	An engineer should check for airlocks or system sludge
F19	Mains voltage too low	Check plug sockets; contact your electricity provider

 

Important Safety Note: 

If your Vaillant boiler is showing a fault code not listed here or the same code keeps reappearing, Maintracts Services is here to help. Our Gas Safe engineers diagnose and repair all types of Vaillant boiler faults across London. Call 020 8682 2244 or book a visit online. 

Also Read: Glow-Worm Boiler Error Codes      

Trust Maintracts Services For Reliable Vaillant Boiler Repairs

Don't let a fault code leave you in the cold. Whether it's low pressure, ignition failure, or a sensor error, Maintracts Services is here to help with expert Vaillant boiler repairs across London. With over 50 years of experience, we are thoroughly familiar with these systems. From emergency callouts to reliable diagnostics, our Gas Safe-registered engineers get things running smoothly and quickly. Here’s why you should choose Maintracts Services: 

• Trusted Vaillant boiler specialists in London 
• Same-day service across London 
• Transparent, upfront pricing with no hidden fees 
• Accredited Vaillant repair specialists 

Call 020 8682 2244 or book your repair online and get your boiler sorted by the experts.