Brr! It’s a proper chilly morning, and just when you’re ready for a hot cuppa and a warm shower, your Vaillant boiler flashes the F61 fault code. No heating, no hot water, and a whole lot of “oh no!”
A Vaillant F61 fault code usually points to a gas valve actuation/communication problem - meaning the boiler’s control board (PCB) can’t correctly control the gas valve.
Put simply: the boiler’s “brain” and the gas valve aren’t speaking properly, so the boiler shuts down for safety (no heat, no hot water, no joy).
Do this now (safe homeowner checks):
[1] Check whether you have gas supply
Try another gas appliance (hob/fire).
If nothing works: you may have a property gas supply / meter / credit issue.
If other gas appliances work: the issue is likely boiler-side (gas valve/PCB/wiring).
[2] Reset the boiler once
Use the reset function once (follow your manual).
If F61 returns, don’t keep resetting - repeated resets can hide an ongoing fault.
[3] If you smell gas, stop immediately
Open windows/doors
Don’t use switches or naked flames
Leave the property if needed
Call the National Gas Emergency Service: 0800 111 999
If there’s any gas smell, this isn’t a “try a few steps” moment.
🔑 Key takeaways:
F61 means a gas valve control/actuation issue (PCB can’t reliably control the gas valve).
Most common causes: faulty gas valve, wiring fault, or PCB issue.
DIY is limited: gas supply check + one reset only.
Call a Gas Safe engineer if it persists - internal repairs are not DIY-safe or legal.
If your boiler is older and repair costs stack up, replacement may be better value.
What Does the Vaillant F61 Fault Code Mean?
F61 indicates a fault with the fuel/gas valve actuation, or the communication/control between the PCB and the gas valve.
The gas valve controls gas flow to the burner. If the PCB can’t command it correctly (or can’t confirm it’s behaving properly), the boiler locks out as a safety measure.
Translation: your boiler would rather shut down than take a risk - and honestly, fair enough.
Can You Fix the Vaillant F61 Fault Yourself?
Realistically: no.
F61 involves gas components and control electronics, so only a Gas Safe registered engineer should diagnose and repair it.
What you can safely do:
Check other gas appliances work (rules out supply issues)
Reset the boiler once
If you’re on prepay, check your meter has credit
If you smell gas, follow emergency steps (don’t troubleshoot)
What you should not do:
Don’t open the boiler casing
Don’t touch wiring, valves, or internal components
Don’t keep resetting again and again
This isn’t “changing a tap washer.” It’s more “don’t touch the dragon.”
Common why the Vaillant F61 error code appears
A Gas Safe engineer will normally check these areas first:
Gas Supply Issue
One of the less common - but still possible - causes of an F61 error code is a gas supply fault, i.e. no gas supply to your boiler
It’s the boiler equivalent of trying to start a car with an empty petrol tank - nothing’s going to happen!
You can check if this is the issue by testing other gas appliances in your home, like your cooker or fire. If they’re not working either, you’ve likely got a gas supply problem.
This could be due to your energy company cutting off the supply, gas works in your area, or simply forgetting to top up your meter (if you have a prepaid one).
Looking to pay for your new boiler monthly? Refer to our boilers on finance guide.
Cost to fix: £50–£100
Faulty Gas Valve
A faulty gas valve is one of the most common culprits behind the F61 error.
Image showing a standard gas valve
The gas valve’s job is to control the flow of gas into the boiler. If it’s not working, no gas reaches the burner, and your boiler can’t heat your water. The fault could be mechanical (the valve is stuck) or electrical (a wiring issue).
Unfortunately, we can’t help with Aunt Marge’s dodgy gas valve after a Sunday roast - just keep her away from the beans!
Cost to fix: £200–£320
Wiring Fault
The gas valve and PCB are connected by a wiring harness, and if there’s a problem here, communication breaks down.
Image showing standard wiring
Think of the PCB as your boiler’s brain and the wiring as its nervous system. A loose or damaged wire is like a bad phone line - messages don’t get through, and the gas valve doesn’t know what to do, causing the boiler to shut off.
Cost to fix: £100–£500
Is your boiler leaking or losing pressure? Use our quick and easy tool to get your fixed price boiler replacement.
Mechanical Fault
Sometimes, the gas valve itself has a mechanical issue. Over time, wear and tear can cause the valve to stick, meaning it can’t open or close properly to let gas through.
Image showing a standard gas valve
A sticky gas valve is like a rusty gate - it just won’t budge when you need it to. This stops the gas flow, and your boiler locks out, displaying the F61 code.
Cost to fix: £150–£300
PS: You may be interested in Gas Engineer Allen Hart explaining the most common boiler problems and how you can resolve them in the video below:
PCB Fault
The printed circuit board (PCB) is the control centre of your boiler, managing all its components, including the gas valve.
Image showing a standard PCB
If the PCB is faulty, due to a short circuit or component failure, it can’t send the right signals to the gas valve. It’s like trying to run a team with a manager who’s lost their voice - nothing gets done, and the boiler shuts down.
For Father’s Day, how about a card that says, “Dad, you’re the PCB of our family”? We’ll take the credit for that one.
Cost to fix: £360–£500
Check our new boiler costs guide, and to get an instant quote, use our fixed-price boiler quote tool.
How a Gas Safe Engineer Will Fix the F61 Fault
A Gas Safe engineer will follow a step-by-step process to diagnose and fix the F61 fault. Here’s what they’ll likely do:
Inspect the Gas Valve: They’ll check if the valve is stuck or broken. A seized valve might be freed, but a faulty one will need replacing, costing around £200–£320.
Check the Wiring: The engineer will look for loose, damaged, or corroded connections. Minor wiring fixes are quick, but a new harness might be needed.
Test the PCB: If the valve and wiring are fine, the PCB could be the culprit. A faulty PCB can cost up to £500 to replace, and for older boilers, a new unit might be a better bet.
Verify Gas Supply: They’ll ensure gas pressure is adequate and there are no blockages.
Full Boiler Check: A good engineer will inspect other parts, like the pump or sensors, to catch any issues that could cause future faults.
Repair costs depend on the problem. Labour typically runs £30–£60 per hour, plus parts. A gas valve might set you back £200–£320, while a PCB could be £360–£500. If parts need ordering, you might be without heat for a day or two.
Costs to Fix the Vaillant F61 Fault Code
Costs vary by model, region, access, and what actually failed - but these ranges are a reasonable guide:
Gas supply issue - £0–£100 (credit/supplier visit/quick fix)
Gas valve replacement - ~£200–£320
Wiring/harness repair - ~£100–£500
PCB replacement - ~£360–£500+
Labour - typically £30–£60/hour (region-dependent)
If your boiler is older, paying £400–£500 for a PCB can be the point where replacement suddenly looks… oddly attractive.
How to Prevent the Vaillant F61 Fault Code
Nobody wants a repeat of the F61 drama. Here’s how to keep your boiler in top shape:
Annual Servicing: A yearly check-up by a Gas Safe engineer can spot issues like worn valves or loose wiring before they cause trouble. It also keeps your warranty valid.
Check for Leaks: Water leaks can damage wiring or components, so keep an eye out for drips around your boiler or pipes.
Ensure Ventilation: Proper airflow prevents overheating, which can stress the PCB and other parts.
Consider a New Boiler: If your boiler’s over 10 years old, a new, efficient model could save you from frequent repairs.
Do You Need A New Boiler?
In some cases, replacing a boiler can make more financial sense than continuing to repair it. Here are the key factors to consider:
Age of the Boiler - If your boiler has surpassed its average lifespan (typically beyond 15 years) and is no longer covered by the manufacturer’s warranty, replacing it may be a more cost-effective option to avoid recurring repair expenses.
Repair Costs - When the cost of repairing the boiler exceeds 50% of the price of a new one, it’s usually more financially sensible to invest in a replacement rather than continuing with costly repairs.
Frequency of Breakdowns - If your boiler is breaking down more frequently, it’s often a sign of significant wear and tear and it is beyond economical repair. In such cases, replacing the boiler can help avoid mounting repair costs and the inconvenience of ongoing issues.
Energy Efficiency - Older boilers tend to be far less efficient than modern models, leading to higher running costs. Upgrading from a G-rated to an A-rated boiler could save you up to £385 per year in energy bills, making replacement a financially smart decision in the long run.
By carefully weighing these factors, you can determine whether replacing your boiler offers better value and peace of mind compared to continued repairs.
Learn all about combi boilers in our what is a combi boiler.
Get a Quote for a New Boiler Today
The best way to resolve the F61 error code is to seek the help of a registered Gas Safe Engineer, who will be able to diagnose and repair whatever is causing the F61 code to be displayed.
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