Protherm F.63 Fault Code: Causes, Fixes & Repair Costs
What does the Protherm F.63 fault code mean?
The F.63 code appears on Protherm boilers when the main printed circuit board (PCB) has detected a problem with its internal EEPROM — the small memory chip that stores the boiler's configuration settings and operational data. When this memory becomes corrupted or fails to respond correctly, the boiler locks out to prevent unsafe operation. You may see the letter 'F' flashing on the display alongside '63'. Note that F.63 sits within the F.6x family of PCB and electronics faults: F.61 indicates no signal reaching the gas valve; F.62 means the gas valve is receiving an incorrect close signal; F.64 relates to rapid, erratic changes in the flow and return sensor readings; and F.65 means the control board itself is overheating. It is not uncommon for a single underlying fault — such as a damaged wiring loom or failing PCB — to trigger several of these codes at different times, so keep a note of all codes you have seen.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- EEPROM data corruption on the PCB Common
The most frequent trigger. The EEPROM chip on the main board stores the boiler's settings and recent fault history. If that data becomes corrupted — due to age, electrical stress, or a voltage spike — the board cannot verify its own configuration and raises F.63.
- Failing or failed main PCB Common
Over time, electronic components on the control board degrade. Dry solder joints, failed capacitors, or a general breakdown of the board's electronics can all produce an EEPROM-related fault code even when the chip itself is technically intact.
- Loose or damaged wiring to the control board Sometimes
A loose connector, chafed cable, or corroded terminal feeding the PCB can interrupt communication between the board and its components, causing the EEPROM error to appear intermittently or persistently.
- Power surge or unstable mains supply Sometimes
A sudden spike or sustained fluctuation in the mains voltage can corrupt the EEPROM's stored data or damage the board's electronics directly. If F.63 appeared after a power cut or electrical storm, this is a plausible cause.
- Incorrect boiler-type configuration stored in memory Rare
Protherm boards store the boiler's type and variant in their configuration memory. If this setting is wrong — for example, after a previous board swap — it can cause the EEPROM check to fail and trigger F.63.
How to fix it
- Reset the boiler and observe whether the fault clears DIY safe
Press the reset button (or use the controls described in your boiler's manual — on some Protherm models this involves holding 'OK' until '0' appears). Wait at least five minutes with the boiler fully powered off before switching it back on. If the boiler fires up and runs normally, monitor it closely over the next 24–48 hours. Limit resets to two or three attempts; repeatedly resetting without resolving the root cause is not effective and should be avoided.
- Check that the mains power supply to the boiler is stable DIY safe
Verify that the boiler's isolator switch is properly on and that no other appliances on the same circuit are causing issues. If you experienced a power cut or electrical event shortly before F.63 appeared, note this down to tell your engineer — it is a useful diagnostic clue.
- Have a Gas Safe engineer inspect the wiring and cable connections to the PCB Gas Safe engineer
Loose, corroded, or damaged wiring between sensors, ancillary components, and the main board is a known trigger for F.6x faults. An engineer will check every connector at the board and along the loom, re-seating or replacing any suspect connections. This is not a homeowner task — the board is an electrical component inside a gas appliance.
- Have a Gas Safe engineer verify the boiler-type configuration settings Gas Safe engineer
The engineer can access the service menu to confirm the correct boiler variant is set in the board's configuration. An incorrect setting left over from a previous repair can cause the EEPROM check to fail repeatedly. Correcting it may resolve the fault without needing to replace any parts.
- Have the PCB assessed and replaced or reconditioned if necessary Gas Safe engineer
If wiring and configuration checks do not resolve the fault, the PCB itself is almost certainly the cause. A Gas Safe engineer (or a specialist boiler electrician working with one) will replace the board with a new or reconditioned unit. Reconditioned PCBs — where failed components are replaced and dry joints re-soldered — are a cost-effective alternative to a brand-new board and typically come with a one-year warranty. Make sure you receive a written quote before authorising any parts.
- Contact a Gas Safe registered engineer if the fault persists or you have not yet done so Gas Safe engineer
F.63 is an electronic lockout that almost always requires professional diagnosis. If the boiler will not reset, has returned the fault multiple times, or you are unsure of the cause, call a Gas Safe registered engineer. They can confirm whether the PCB needs replacing, source the correct part for your Protherm model, and carry out the work safely and legally.
Parts you may need
- Protherm main PCB (control board) — new · from £280
- Protherm main PCB — reconditioned/exchange unit · from £140
- PCB wiring loom / connector set · from £35
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £300–£450, depending on the underlying cause.
Frequently asked questions
Can I fix Protherm F.63 myself by resetting the boiler?
A single reset is always worth trying — occasionally a transient power fluctuation causes a one-off EEPROM error that clears on restart. However, if the fault returns after one or two resets, there is an underlying hardware problem (almost always the PCB or its wiring) that a reset cannot fix. At that point you need a Gas Safe registered engineer. Do not keep resetting repeatedly, as it will not help and could mask a more serious issue.
How much does it cost to fix Protherm F.63 in the UK?
Most people with this fault end up paying between £300 and £450 all-in, which typically covers the engineer's call-out and labour plus a replacement PCB. A new PCB alone generally costs £180–£400 depending on the exact Protherm model; a reconditioned exchange board is usually cheaper (often around £100–£160 for the part) and can bring the total repair cost down. Always get a written quote before work begins.
Is it worth repairing a Protherm boiler with an F.63 fault, or should I replace it?
If your boiler is under ten years old, a PCB replacement at £300–£450 is usually a sensible investment — the rest of the boiler may have many years of life left. If the boiler is older than ten to twelve years, it is worth getting a replacement quote alongside the repair quote, since other components (heat exchanger, pump, diverter valve) may be approaching the end of their lifespan too. A Gas Safe engineer can give you an honest assessment of the boiler's overall condition.
What is the difference between F.63 and the other F.6x codes on my Protherm?
F.61 means the gas valve is not receiving a control signal; F.62 means the gas valve is receiving an incorrect signal to close; F.63 is the EEPROM/memory fault covered on this page; F.64 indicates the flow and return temperature sensors are showing erratic, rapidly changing readings; and F.65 means the control board is overheating. These codes can appear separately at different times but may all stem from one faulty component — such as a degraded PCB or damaged wiring loom — so it is worth telling your engineer every code you have seen.