If your Vaillant ecoTEC Pro, ecoTEC Plus, ecoFIT Pure or older ecoMAX is locked out on F62, you’ll have no heating, no hot water and a red flashing display. F62 means the gas valve has taken too long to close after the burner switched off, so the boiler has gone into safety lockout.
This fault hits thousands of UK homes every winter, especially on boilers made between 2011 and 2018.
What Actually Causes F62 on Vaillant Boilers
Gas Valve Becoming Slow or Sticky
Age, heat cycles and microscopic debris make the solenoid or stepper motor sluggish.
Corroded or Loose Gas-Valve Wiring Harness
The multi-pin connector on top of the valve suffers from years of expansion and contraction.
Condensate Leaking onto the Main PCB
A tiny drip from the sump or trap lands on the gas-valve driver circuit – the number-one cause on boilers over 8 years old.
Faulty Driver Circuit on the PCB Itself
Dry solder joints or component failure on the board.
Safe DIY Checks (Very Limited)
Reset the boiler by holding the spanner/reset button for 5 seconds.
Look underneath for any drips or puddles – a visible condensate leak often triggers F62.
That’s all you’re legally allowed to do.
When You Must Call a Gas Safe Engineer
F62 is 99 % of the time a gas-side or PCB fault. Only a registered engineer can test or replace the gas valve, change the wiring harness, dry out or replace the PCB, and carry out the mandatory combustion check afterwards. Always check they’re on the Gas Safe Register.
Typical Repair Costs
- Wiring harness only: £130–£190
- New gas valve: £340–£480 fitted
- New main PCB: £420–£620 fitted
- Fixed-price F62 repair (many Vaillant specialists): £380–£580
How to Prevent F62 Happening Again
Annual servicing by a Vaillant-trained engineer catches early sump leaks.
Fit a condensate pump or pro kit in loft installations.
Use a magnetic filter and quality inhibitor from day one.
Frequently Asked Questions About Vaillant F62
What’s the difference between F61 and F62?
F61 = the PCB can’t control the gas valve at all. F62 = the valve is slow to close after the burner stops. The repair is usually identical – valve, harness or PCB.
Will resetting fix F62 permanently?
Almost never. It might clear for a few seconds or minutes, then it’s straight back.
Is F62 covered by my Vaillant warranty?
Yes – provided the boiler is still within its 5–10 year warranty and has a full, annual service history by a Vaillant-approved engineer.
My boiler is only 7 years old – why has this happened already?
Condensate dripping onto the PCB is the usual culprit on 2012–2016 ecoTEC Plus models. Still fully warranty if serviced every year.
Repair or replace?
Under 10 years and good service history → repair (usually £400–£550).
Over 12 years or needs valve + PCB → a new boiler is often cheaper and more efficient.
Still staring at F62 right now? Drop your exact model and year in the comments and we’ll tell you the most likely fix and realistic price in your area.
With years of experience in boilers and home improvements in general, Myles Robinson is a passionate advocate for making home heating simpler, safer, and more affordable for households across the UK. With years of experience in the heating industry, Myles combines hands-on knowledge with a focus on customer-first service, helping homeowners choose the right boiler, understand their systems, and keep their heating running efficiently all year round. His articles break down complex topics into clear, practical advice you can trust.