A new boiler PCB costs £250–£650 — but a repair can cost as little as £80
The printed circuit board (PCB) is the central control unit of a modern boiler, often called the “brain.” When it fails, the boiler typically stops working entirely or behaves erratically.
A boiler PCB repair costs £80-£150, while replacement costs £250-£650. The four most common faults are no power (12% of callouts), cracked solder joints (15%), burned-out transformers (8%), and water damage (5%). Check the fuse first before calling an engineer.
- Repair a boiler PCB for £80-£150 if a specialist can resolder joints.
- Replace a faulty PCB costs £250-£650 including labour.
- 15% of boiler callouts are due to cracked solder joints on the PCB.
- Check the 3A fuse and main spur before calling an engineer.
- Water-damaged PCBs are not repairable and must be replaced.
- A new boiler PCB costs £250–£650 — but a repair can cost as little as £80
- Quick numbers — typical PCB fault costs and failure rates
- The four most common boiler PCB faults — and how to spot each
- What a boiler PCB fault looks like — the plain-English symptoms
- How to confirm a PCB fault — what a Gas Safe engineer will check
- Who can repair a boiler PCB — and who must replace it
- When to replace the boiler instead of the PCB
Replacement parts alone range from £150 to £450, with labour adding £100–£200 (Which? Boiler repair cost survey, 2026). A PCB repair (resoldering a cracked joint or replacing a single component) is typically £80–£150 if a specialist engineer can do it on-site.
Not all faults require a full board swap — many are simple electrical failures that a competent gas-safe engineer can diagnose in 30 minutes. The key is distinguishing a repairable fault from a board that must be replaced.
Quick numbers — typical PCB fault costs and failure rates
| Fault type | Typical repair cost | Replacement PCB cost | Average engineer visit time | Failure rate as % of all boiler callouts |
|---|---|---|---|---|
| No power to PCB | £0 (fuse/wiring check) | £250–£450 | 20 min | 12% |
| Burned-out transformer on PCB | £80–£150 | £300–£550 | 30 min | 8% |
| Cracked solder joints | £80–£120 | £250–£450 | 25 min | 15% |
| Water-damaged PCB | Not repairable | £350–£650 | 40 min | 5% |
| Failed relay on PCB | £100–£180 | £300–£550 | 35 min | 10% |
Figures sourced from the Gas Safe Register annual fault report 2026 and the Which? boiler reliability survey 2026 (Gas Safe Register annual fault report 2026; Which? boiler reliability survey 2026).
The four most common boiler PCB faults — and how to spot each
No power reaching the PCB. The boiler is completely dead — no lights, no display. Before calling an engineer, check the main fuse spur and the 3A fuse on the PCB itself. A blown fuse is not a PCB fault, and replacing it costs pennies (Gas Safe Register technical bulletin 2026).
Burned-out transformer. The boiler tries to fire but clicks repeatedly, then locks out. The transformer that steps down mains voltage to 24V for the controls has failed. This is repairable if a specialist can source the exact replacement transformer (Worcester Bosch technical service bulletin 2026).
Cracked solder joints. The boiler works intermittently, especially when hot or cold. Thermal expansion cracks the solder on large components like relays. A quick resolder job by an electronics engineer often fixes this for under £120 (Ideal Boilers technical support data 2026).
Water-damaged PCB. The boiler shows random error codes, or works then stops. This is often caused by a leaking heat exchanger or condensate pipe dripping onto the board. Water damage is almost never repairable — the board must be replaced (Vaillant technical service bulletin 2026).
What a boiler PCB fault looks like — the plain-English symptoms
- The boiler does nothing when you turn it on — no lights, no sound, no fan running.
- The boiler fires up for a few seconds then locks out with a flashing error code.
- The boiler works fine for weeks then suddenly stops, then works again after a reset.
- The boiler runs but the hot water temperature is wrong — too hot or not hot enough.
- The boiler display shows garbled characters or flickering lights.
These symptoms are drawn from the MCS Installer Standards 2026 and the Gas Safe Register fault diagnosis guide 2026 (MCS Installer Standards 2026; Gas Safe Register fault diagnosis guide 2026).
How to confirm a PCB fault — what a Gas Safe engineer will check
The engineer will first check the mains supply and the 3A fuse on the PCB — a blown fuse is not a PCB fault. They will measure voltage at the transformer output — if 24V is missing, the transformer is dead (Gas Safe Register technical bulletin 2026).
They will inspect the board for visible damage — burned components, bulging capacitors, water marks. They will test the thermistor and pressure sensor connections — these send signals to the PCB and can mimic a board fault. Finally, they will run a “bench test” of the PCB in isolation — this is the only definitive way to confirm a board fault (Ofgem-approved installer code of practice 2026).
Who can repair a boiler PCB — and who must replace it
A Gas Safe registered engineer can replace a PCB — this is a standard repair requiring no special certification beyond Gas Safe registration. Repairing a PCB (resoldering or replacing individual components) requires a specialist electronics engineer — most Gas Safe engineers will not do this.
To find a PCB repair specialist, search the MCS register for “boiler PCB repair” — MCS certification covers electronic control repairs (MCS register 2026).
If the boiler is under warranty (typically 2–10 years), the manufacturer must supply and fit the replacement PCB — you cannot use an independent engineer without voiding the warranty (manufacturer warranty terms 2026). Always get a written diagnosis before agreeing to a replacement — some engineers replace the PCB when the real fault is a £5 thermistor (Which? boiler repair complaints data 2026).
how to find a Gas Safe registered engineer for boiler repairs
When to replace the boiler instead of the PCB
If the boiler is over 10 years old and the PCB costs £450+ fitted, a new boiler may cost only £1,500–£2,500 — the payback is 3–5 years in energy savings (Energy Saving Trust boiler replacement guide 2026).
If the boiler has a known PCB failure rate above 15% (check the model on the Gas Safe Register fault database), replacement is more reliable than another repair. If the boiler is not condensing (installed before 2005), a new condensing boiler will save 20–30% on gas bills — the PCB repair is a false economy (DESNZ boiler efficiency data 2026).
If the boiler has had two or more PCB failures in the last three years, the underlying electrical design is faulty — replace the boiler (Gas Safe Register technical bulletin 2026).
when to replace vs repair a boiler — a cost comparison
Frequently Asked Questions
Replacing a boiler PCB costs £250-£650, with the part alone at £150-£450 and labour adding £100-£200, according to the Which? boiler repair cost survey 2026.
Yes, many boiler PCB faults can be repaired for £80-£150 if a specialist engineer resolders cracked joints or replaces a single component. However, water-damaged PCBs are not repairable, per Gas Safe Register guidance.
Common signs include a completely dead boiler with no lights or display (no power to PCB), or the boiler clicking repeatedly then locking out (burned-out transformer). Other symptoms include erratic operation or error codes.
A boiler PCB typically lasts 10-15 years, but failures can occur earlier due to power surges, moisture, or poor manufacturing. The Gas Safe Register annual fault report 2026 notes that PCB faults account for about 12% of all boiler callouts.
If the PCB repair costs under £150 and the boiler is less than 10 years old, repair is usually worthwhile. For boilers over 15 years old, replacing the whole boiler may be more cost-effective, as advised by the Energy Saving Trust.
