Boiler PCB Failure
Random lockouts, a display that behaves oddly, or a boiler that ignores the controls entirely..
Random lockouts, a display that behaves oddly, or a boiler that ignores the controls entirely.
What is actually going on
Random lockouts, a display that behaves oddly, or a boiler that ignores the controls entirely.
The realistic causes, in order
Water ingress onto the board from a weeping heat exchanger seal or an external leak dripping through the case Dry solder joints and heat-stressed relays after many years of switching the pump and fan Damage from a mains surge or from an incorrectly wired external control added later
What we test on site
Board condition under inspection — tracking marks, swollen capacitors, corrosion around the relay legs Switched live and permanent live at the terminal strip to prove the fault is inside the board, not upstream Every sensor input in turn, because a failing sensor can imitate a board fault
Safe checks to make with a suspected PCB failure
- Note whether the fault is random or repeats at the same point in the cycle — that distinction matters
- Check the room thermostat batteries before assuming the boiler is at fault
- PCB replacement must be followed by re-commissioning to the manufacturer's data, including a gas rate and combustion analysis. It is not a plug-and-play part.
Who does the work
- Gas Safe registered engineers — registration 554328
- Worcester Bosch accredited installer
- John The Plumb Ltd, company registration 10026483
Get a suspected PCB failure diagnosed properly
On an older appliance a PCB is often the point where a repair-versus-replace conversation becomes genuinely worth having.
Questions we get asked
What causes a suspected PCB failure on a gas boiler?
Water ingress onto the board from a weeping heat exchanger seal or an external leak dripping through the case
What normally puts a suspected PCB failure right?
On an older appliance a PCB is often the point where a repair-versus-replace conversation becomes genuinely worth having.
Is it safe to keep using the system with a suspected PCB failure?
PCB replacement must be followed by re-commissioning to the manufacturer's data, including a gas rate and combustion analysis. It is not a plug-and-play part.