Error .14

Safety precautions:

1) Do not attempt gas valve, burner or mains-electrical repairs unless you are a Gas Safe registered engineer. Working on internal boiler parts can be dangerous.

2) Before opening the boiler casing, switch OFF the electrical supply at the isolator and turn off the gas supply if instructed by an engineer. Allow the boiler to cool. Use insulated tools and avoid touching live circuits.

3) If you are unsure or uncomfortable at any point, stop and call a Gas Safe engineer.

Initial checks a homeowner can do (safe, non-intrusive):

1) Note the exact error (.14 / F.14) and when it appeared (after a power cut, after work, during demand etc.).

2) Try a single reset: press and hold the boiler reset button or follow the manual’s reset procedure. If the fault does not clear or returns immediately, do not keep resetting repeatedly.

3) Check the system water pressure on the boiler gauge; if pressure is very low (<1 bar) top up following the manufacturer’s instructions, then reset. Low pressure can cause other faults but .14 remains an NTC issue.

4) Visually inspect around the boiler for obvious signs: water leaks, corrosion, damaged external wiring to the boiler, or signs of impact to the flue or casing. Do not open the boiler if you are not competent.

Diagnostic and fix steps (for a qualified engineer or experienced technician):

1) Verify fault memory and freeze-frame data from the boiler if available to confirm which sensor or channel is implicated (flow, return, cylinder/DHW). Documentation or service mode will show which NTC input is out of range.

2) Isolate mains and gas, remove the boiler outer casing following the manufacturer’s instructions.

3) Visually inspect NTC plugs and harness: look for loose connectors, corrosion, water ingress, chafed or broken wires and signs that plugs are not seated fully on the sensor bosses. Re-seat any loose plugs and secure wiring looms.

4) Using a multimeter, measure resistance of each suspect NTC at room temperature at the sensor connector and at the PCB connector to check for wiring continuity and correct sensor resistance. (Note: many Vaillant NTCs are nominally ~10 kΩ at 25°C but confirm exact spec from the manual or part datasheet.)

5) Check for short circuits to earth or between sensor wires and inspect wiring continuity through the harness. If there is a short or open in the harness, repair or replace the harness as required.

6) If a sensor shows open circuit or short, replace that NTC sensor. The Ecomax Pro guidance often recommends changing flow and return NTCs together to speed diagnosis — replacing multiple sensors can prevent repeated call-outs.

7) If sensors and harness check OK, test the PCB input channel for the sensor: check connector pins, wiring at the PCB, and measure the input with the sensor connected. If PCB input is defective or floats, further PCB diagnostics or replacement may be required.

8) After repair or replacement, reassemble, restore gas and power, and run the boiler through a controlled start-up and functional test. Confirm no further error codes and that heating/hot water operate normally.

When to call a professional:

- If the fault persists after a reset and basic visual checks.

- If you need to open the boiler casing, test sensors electrically, or replace sensors, wiring or PCB. These tasks involve live circuits, gas safety and appliance commissioning and must be done by a Gas Safe registered engineer.

Important notes:

- Replacing NTC sensors is a common fix for .14 errors; many engineers will recommend changing flow and return sensors together to reduce repeat faults.

- Do not repeatedly reset the boiler as a long-term workaround; repeated lockouts can mask an underlying safety issue and risk damage.

- Keep a record of the fault and any work done for the engineer who attends next, including whether the fault is intermittent or permanent and any recent events (power cuts, work to plumbing/electrics, leaks).