Error F0 238

Safety precautions:

- If you smell gas or suspect a gas leak: do not operate electrical switches, do not use naked flames, open windows and doors, leave the property immediately and call the gas emergency service (in the UK phone 0800 111 999) and a Gas Safe engineer. Do not try to repair gas components yourself.

- If you are unsure or uncomfortable with any step below, stop and call a qualified Gas Safe engineer. Working on gas appliances can be dangerous.

- Do not repeatedly reset the boiler. One short reset to see if the fault clears is acceptable, but multiple resets can mask a developing safety issue.

Initial homeowner checks:

1. Note the exact fault code displayed (F0 238) and any other codes or symptoms. Photograph the display if possible for the engineer.

2. Check boiler water pressure at the boiler gauge. It should normally be around 1.0 to 1.5 bar when cold. If pressure is below 1 bar, top up using your filling loop following your boiler manual if you know how; low pressure can cause related faults.

3. Verify gas supply to the property: try lighting another gas appliance such as the hob. If no other appliance has gas, contact your gas supplier.

4. Check for the smell of gas. If present, follow the emergency steps above.

5. Try a single boiler reset using the boiler reset button or controls as described in the manual. Wait to see if the code returns. If the code reappears immediately, stop further resets.

Basic visual checks you can safely do:

1. With the boiler powered down and isolated at the mains switch, look for any obvious loose or disconnected wiring at external connectors and plug connections (do not open sealed or gas-containing components). Re-seat accessible plug connections if you are comfortable doing so and then power up to test once.

2. Check the boiler flue and condensate pipe are unobstructed and intact; blockages can create unrelated faults but are simple to rule out visually.

Specific diagnostic and next steps (professional actions expected):

1. If the code persists after the basic checks, the likely causes are faulty gas valve coils, a leaking or failed gas valve, or a control/burner control unit fault. These components require specialist testing and replacement.

2. A Gas Safe engineer will perform safe gas pressure checks, test and measure the gas valve coil resistances, inspect for valve leaks, verify flame sensing and ignition components, and check communications between the control box and burner control unit. They will also check wiring harnesses and connectors inside the boiler under safe isolated conditions.

3. If the gas valve or control unit is found to be faulty, the engineer will replace the defective part and run commissioning and safety checks, including leak tests and burner performance checks.

When to call a professional and what to tell them:

- Call a Gas Safe registered heating engineer if the fault remains after your basic checks, if you detect any gas smell, if the F0 238 returns after a single reset, or if you are not confident performing the initial checks. Provide the engineer with the exact fault code (F0 238), what you have already checked (pressure, gas supply, reset attempts), any other codes or symptoms, and photo(s) of the boiler display and serial number if possible.

Important final note:

- Do not attempt to dismantle, test, or replace the gas valve coils or the control/burner control unit yourself. These are gas safety critical parts and must be worked on by a Gas Safe registered engineer. Your priority should be safe isolation and contacting a qualified professional when basic checks don't clear the fault.