f28 fault on boiler - what is it & how to fix it!

f28 fault on boiler - what is it & how to fix it!

Understanding and Resolving the Vaillant F28 Fault: A Comprehensive Guide

Introduction: Encountering a Vaillant F28 fault in your boiler can be distressing, especially in the colder months. This guide delves deep into the F28 error, offering detailed insights and solutions.

Basically F28 is an ignition lock-out fault. 

Quick Reference Table:

Fault Code Meaning Initial Checks Professional Action Needed
F28 Failure in ignition sequence Check gas supply, ignition components Yes, if issue persists

In-Depth Analysis & potential causes of the Vaillant F28 Fault:

Gas engineer common sense: Hi my names Lee from the boiler experts, the F28 can be a tricky one, it means your boiler has failed on ignition, it's tried to ignite 3 times and has not succeeded. To be honest, if it's freezing outside check the condense if it's external! Try resetting the boiler and listening, if it gurgles on trying to ignite, usually thats a giveaway! In my experience this fault is usually a blocked condense or an ignition probe issue but of course it can be a lot of things, listed below. It is a fault where I would recommend a gas safe engineer. 

Gas valve wiring: Faulty or loose wiring can disrupt communication between the gas valve and the PCB, leading to the F28 fault. Repairing this is usually a quick and cost-effective fix, starting from around £100. Note: this is very rare! 

Gas Valve Function: Over time, gas valves may get stuck or wear out. If partly closed, they restrict gas supply, triggering the F28 error. Repairing or replacing a faulty gas valve can cost about £300 - £400.

Printed Circuit Board (PCB): The PCB is the heart of your boiler, coordinating its electrical components. If the PCB is faulty, it may not send correct signals to the gas valve, causing the F28 code. PCB repairs or replacements can cost up to £500.

Condensate Blockage: Blockages in the condensate pipe, often due to freezing in winter, can trigger the F28 error. A Gas Safe engineer can defrost and fix this issue for £50-100. Newer models like the Worcester Bosch Greenstar Range have features to prevent such blockages.

Faulty Vaillant Electrodes: Worn-out electrodes fail to ignite the gas, leading to the F28 fault. Replacement of these parts can cost several hundred pounds.

Gas Supply to Your Home: A simple check to see if other gas appliances work can determine if there's a gas supply issue to your home. If there's a supply problem, contact your energy supplier.

General combustions issues: Sometimes a lack of servicing can cause blockages in the heat exchanger, burner issues can also cause this fault! 


    F28 can be simple problem like a blocked or frozen condense but it can also be a complicated combustion, PCB or gas valve issue, it's a bit of a Russian roulette fault! 

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