Modern boilers rely on electronic controls, and the Printed Circuit Board (PCB) ties everything together, including ignition, fan checks, gas valve signals, and the safety routines that keep your home protected. When the PCB plays up, you’ll often see lock-outs, odd error codes or a boiler that refuses to start.
- What it does: Acts as the boiler’s “brain”, coordinating ignition, fan and gas-valve signals while monitoring sensors for safe operation.
- Why it matters: If the PCB fails, the boiler can lock out or behave unpredictably — an immediate comfort and safety issue.
- When it goes wrong: Age-related wear, water ingress/condensation, vibration, or earlier manufacturing/installation faults can all trigger failure.
- Good practice: Switch the boiler off if you smell burning or see a blank/flickering display, then get a Gas Safe registered engineer to diagnose.
- Repair or replace? Resets are short-term at best; a professional may repair in limited cases, but replacement — including quality refurbished units — is often the sensible fix.
Benefits at a glance
Safer operation
A healthy PCB ensures that safety checks are run appropriately, and the boiler shuts down when it should.
Fewer breakdowns
Finding and fixing root causes, like leaks and failed components, reduces repeat call-outs.
Cost-effective options
Tested refurbished PCBs can restore function at a lower cost and with less waste than a brand-new part.
Clear next steps
A structured diagnosis prevents guesswork and part-churning.
Common symptoms of a PCB fault
- Blank, flickering or erratic display despite a good power supply
- Boiler locks out, won’t ignite, or cuts out mid-cycle without a clear mechanical fault
- Ambiguous electronic-control error codes
- Fan/gas-valve not being driven correctly, leading to failed ignition
- Electrical or scorched smells around the casing
If you notice any of the above, switch off the boiler and contact a Gas Safe registered engineer to inspect it safely for a boiler PCB fault.
FAQs
Can a reset fix a PCB problem?
Sometimes, briefly — but recurring faults, electrical smells, or visible damage need professional repair or replacement, not repeated resets.
Are refurbished PCBs reliable?
Yes, when correctly remanufactured and supplied by a reputable source with proper testing and a guarantee.
What usually causes PCB failure?
Moisture ingress, vibration, ageing solder joints/relays, or early-life issues with assembly or protection. An engineer will also check for leaks elsewhere that may have led to damage.
How long does a PCB last?
It varies with usage, maintenance and environment. In well-maintained boilers protected from leaks and condensation, a PCB can last many years.
Should I replace the PCB first, or find the root cause?
Always find the cause. Replacing a PCB without fixing leaks, faulty pumps or heat exchangers risks another early failure.
Need help choosing the right PCB?
Talk to our technical team for plain-English advice on diagnosis and replacement.
WhatsApp (badge): https://wa.me/447834398673
Contact us: Contact Us | National Boiler Spares
Make sure to hire a Gas Safe registered engineer for any diagnosis, installation, or repair work.
