Error F.17

Safety precautions:

- Do not open the boiler casing or probe inside unless you are a trained, qualified engineer. Interior parts carry live voltages and gas components present additional hazards.

- If you will do any external checks, isolate the boiler electrically at the external fused spur or consumer unit before touching wiring or connectors. If you are not competent with electricity, do not isolate or touch anything — call an electrician.

- If you smell gas or suspect a gas leak, turn off the gas supply, ventilate the area, evacuate if necessary and call the gas emergency number and a Gas Safe engineer immediately.

Initial homeowner checks (safe, non-intrusive):

1. Note the exact code and any other symptoms (no fan spin, no ignition clicks, LEDs). Photograph the display.

2. Try a simple reset: switch the boiler off at the external isolator or consumer unit, wait 1–2 minutes, then switch back on and attempt to start. If F.17 reappears, further checks are needed.

3. Inspect the external fused spur/plug (if the boiler uses one) for obvious damage, burning, loose screws or a blown fuse. Do not remove the cover or touch live parts.

4. Check whether other household appliances or lights are behaving oddly (flickering, dimming) which could indicate a wider mains supply issue.

5. If the boiler is supplied from a plug and lead, try the lead/plug on a known-good socket or have a qualified electrician inspect/replace the plug or lead.

Specific diagnostic and fix steps (for qualified personnel):

1. Confirm mains presence and voltage: with the boiler powered and using a calibrated multimeter, measure L–N voltage at the boiler incoming terminals. Expect nominal ~230 V; voltages under ~170 V can trigger faults. Also measure L–E and N–E to check for missing neutral or earth issues.

2. Check polarity: verify live and neutral are correctly connected at the fused spur, boiler terminal block and consumer unit. Look for swapped L/N conductors or loose/corroded terminals.

3. Inspect and test the fused spur, any inline isolator, RCD/RCBO and the consumer unit for tripped devices or damaged connections. Tighten and re-torque terminal screws to correct spec if loose.

4. Check earthing/earth bonding continuity and correct wiring to ensure no floating neutral/earth faults are causing mis-detection.

5. With supply confirmed good, check the fan and ignition transformer supplies and signals. Measure the low-voltage outputs to the ignition transformer (if separate) and confirm the transformer is producing the expected secondary voltage. Reports indicate a faulty ignition transformer has sometimes caused F.17 indications.

6. Inspect the PCB and connector blocks for burned tracks, blown components, or damaged connectors. Replace only if diagnostics indicate PCB failure. Follow manufacturer fault finding flowcharts and wiring diagrams.

7. If a component is replaced (ignition transformer, fan, PCB), re-test the boiler sequence: power up, observe fan purge, ignition attempt, and confirm no F.17 reoccurrence. Carry out full combustion and safety checks after any gas-side work.

When to call a professional:

- If you cannot resolve the fault with the safe, non-intrusive homeowner checks, or if the fault returns after a reset, stop and call professionals.

- For any polarity reversal, missing neutral, or low mains voltage — contact a registered electrician to inspect and correct the incoming wiring at your consumer unit/fused spur.

- For any internal boiler work, ignition transformer replacement, PCB replacement or gas-related checks and repairs — contact a Gas Safe registered engineer. A Gas Safe engineer and an electrician may both be required for a complete and safe repair.

Final note: Do not continue to operate the boiler if the F.17 fault persists. Electrical polarity/voltage issues can damage electronics and create unsafe operating conditions. Let qualified tradespeople diagnose and fix wiring, transformer or PCB faults and then verify the boiler is safe and running correctly.