Glow-worm F62 Fault Code: Causes, Fixes & Repair Costs
What does the Glow-worm F62 fault code mean?
The F62 code on a Glow-Worm boiler signals an electronic fault on the main control board (PCB). The PCB acts as the boiler's central processor — it coordinates every component from the gas valve to the pump — so when it develops a fault the boiler will lock out and stop providing heating or hot water. F62 sits within a family of related electronic fault codes (F61 through F67) that all point to main board issues of varying types; F62 specifically indicates a detected fault within the board's own circuitry or its communication with connected components. Because the root cause is not always a dead PCB — faulty sensors or damaged wiring can trigger the same code — a proper diagnosis by a Gas Safe registered engineer is essential before any parts are replaced.
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
- Moisture or water ingress onto the PCB Common
An internal leak — from the pump seal, a cracked heat exchanger, or a corroded pipe joint — can allow water droplets to reach the PCB. Even small amounts of moisture can cause short circuits or corrosion on the board's solder traces, triggering an F62 lockout. This is one of the most frequent routes to PCB failure on older Glow-Worm appliances.
- Loose or degraded wiring connections Common
Boilers vibrate continuously during operation. Over months and years this can work terminal connectors loose on the loom that feeds the PCB. Heat cycling also causes plastic connectors to become brittle, increasing resistance and producing intermittent or permanent faults that the board logs as F62.
- Age-related component wear Common
Capacitors, relays, and other surface-mounted components on the PCB degrade with age. On a boiler that is ten or more years old, the board itself may simply have reached the end of its reliable service life, with no single identifiable trigger.
- Dry solder joints Sometimes
Manufacturing tolerances or thermal expansion over many heat cycles can cause solder joints on the PCB to crack and lose contact. The resulting intermittent connection may show up as an F62 that clears on reset only to return — a classic sign of a dry joint rather than complete board failure.
- Power surge or electrical spike Sometimes
A mains voltage surge — from a nearby lightning strike, grid switching, or a faulty consumer unit — can damage the sensitive electronics on the PCB. Surge damage sometimes affects other components simultaneously, such as the fan or ignition module, so multiple faults may appear together.
- Faulty sensor sending bad data to the PCB Sometimes
A defective flow temperature sensor, return sensor, or flue thermostat can feed the PCB with out-of-range readings. The board may interpret this as its own fault and throw an F62 rather than a sensor-specific code. An engineer will rule this out before condemning the board.
How to fix it
- Check the boiler display for any additional codes DIY safe
Note the exact code or codes shown. If F62 is accompanied by a separate sensor or pressure code, that information helps an engineer narrow the diagnosis quickly. Take a photo of the display if possible.
- Verify the gas supply is working DIY safe
Check that other gas appliances in your home (hob, fire) are working normally. If there is no gas supply to the property, contact your gas supplier rather than treating the F62 as a boiler fault.
- Attempt a boiler reset — once or twice only DIY safe
On most Glow-Worm models, turn the CH control knob to the reset position (marked with a power symbol), wait approximately 30 seconds, then turn it back to your desired temperature setting. If the boiler fires and runs normally, monitor it closely. If F62 returns within a short period, do not keep resetting — repeated resets on an electronic fault will not fix the underlying problem and can occasionally mask a developing issue.
- Inspect for visible signs of a water leak DIY safe
Look around the base of the boiler and along visible pipework for damp patches, staining, or drips. Do not touch any electrical components or open the boiler casing. If you find a leak, turn off the boiler and note the location for the engineer — moisture near the PCB is important diagnostic information.
- Do not attempt to open the boiler or touch the PCB Gas Safe engineer
The PCB operates at mains voltage. Removing panels, disconnecting wiring, or attempting to dry out or repair the board yourself is unsafe for an unqualified person and may invalidate any remaining warranty or insurance. Leave all internal inspection to a qualified engineer.
- Have a Gas Safe registered engineer carry out a full diagnosis Gas Safe engineer
An engineer will remove the casing safely, inspect the wiring loom and connectors, test sensors individually, and examine the PCB for visible damage such as burn marks, corrosion, or swollen capacitors. This diagnostic visit typically costs £60–£100 and is the only reliable way to confirm whether the board itself needs replacing or whether a cheaper fix (a connector, a sensor) will resolve the fault.
- Authorise PCB replacement or repair as recommended Gas Safe engineer
If the PCB is confirmed faulty, the engineer will source and fit a replacement unit — a job that typically takes one to three hours. On boilers over ten years old it is worth asking the engineer about the broader condition of the appliance before committing to a PCB replacement, as other components may be close to failure.
Parts you may need
- Replacement PCB (main control board) · from £290
- Wiring loom / connector harness · from £55
- Flow temperature sensor (NTC) · from £20
- Return temperature sensor (NTC) · from £20
- Flue overheat thermostat · from £25
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 £250–£600, depending on the underlying cause.
Frequently asked questions
Can I fix a Glow-Worm F62 fault myself?
Not safely. The F62 code points to a fault involving the boiler's main control board, which operates at mains voltage. Diagnosis and any repair work must be carried out by a Gas Safe registered engineer. The only homeowner actions are checking the gas supply is on, looking for visible leaks, and attempting a single reset. Repeatedly resetting an electronic fault rarely resolves it and can obscure the problem.
Does F62 always mean the PCB needs replacing?
Not necessarily. While a failed PCB is the most serious possibility, engineers frequently find that F62 is triggered by a loose wiring connector, a corroded terminal, or a faulty temperature sensor sending bad data to the board. A proper diagnostic inspection is needed before any parts are ordered. Replacing the PCB without checking those cheaper possibilities first can result in unnecessary expense.
How much does a Glow-Worm PCB replacement cost in the UK?
Most homeowners pay between £450 and £600 for a full PCB replacement including parts and labour in 2025, with prices at the lower end in the North of England and Wales and higher in London and the South East. The PCB component itself typically costs £180–£400 depending on the specific model. If your boiler is still under its manufacturer warranty and has been serviced annually by a Gas Safe engineer, some or all of the cost may be covered — check your warranty documents first.
Should I repair or replace the boiler if I get an F62 code?
If your Glow-Worm is under ten years old and otherwise in good condition, a PCB repair or replacement is usually worthwhile. On boilers aged ten years or more, it is worth asking the engineer for an honest assessment of the appliance's overall condition. Spending £500 on a PCB for a boiler that has several other ageing components approaching end of life may not represent good value, and a new A-rated combi could cut your bills while also coming with a fresh warranty.