Error 114

Safety first: before doing anything isolate electrical power to the boiler at the fused spur or consumer unit and switch off the gas if you will be opening covers or touching internal wiring. Do not attempt internal electrical or gas repairs unless you are a qualified engineer. Wear gloves and eye protection if working outside.

Initial homeowner checks you can safely do:

1. Note the display: record 114 and any other fault codes shown; combine codes give extra clues.

2. Try a simple reset: switch the boiler off for 1 minute, restore power and see if the fault clears. If it reappears, proceed with checks.

3. Inspect the outdoor sensor: locate the small probe or sensor head fixed to an exterior wall. Look for obvious damage, dislodgement, crushed or chewed cable, water ingress, heavy paint/sealant covering the sensor, or snow/ice build-up around it.

4. Trace the cable visually to the point it enters the building. Look for damaged sheathing, cuts, or rodent damage. If the cable is clearly damaged externally, avoid touching exposed conductors; isolate power and call an engineer.

5. Check for loose connections at accessible external terminals or junction boxes (only if the terminals are designed to be user-accessible and there is no need to open the boiler). Ensure connectors are dry and not corroded.

Basic diagnostic steps (for competent DIYers with a multimeter):

1. With boiler powered off and power isolated, you may measure continuity of the sensor cable from the outdoor sensor to the boiler entrance point to confirm the cable is intact. If you find open circuit, the cable or sensor is broken.

2. Measure resistance of the sensor if you can access the sensor head or the boiler sensor terminals. An outdoor thermistor has a characteristic resistance vs temperature curve; consult the boiler service manual for expected resistances at known temperatures (the service manual or sensor resistance table is required). If resistance is wildly out of range (open circuit or short), the sensor is faulty.

3. If you find correct continuity but the boiler still reports 114, the fault may be in the boiler terminal block, wiring harness, or PCB sensor input. Check the terminal block at the boiler entry for loose screws, corrosion or a disconnected plug (only if you are competent and have isolated power first).

4. If you are unsure how to interpret resistance values or the wiring route looks complex, stop and call a professional.

Possible fixes and verification (professional tasks):

1. Replace outdoor sensor: if the sensor shows open/short or visible damage, a like-for-like replacement is required. A qualified engineer will fit the correct thermistor type and length of cable, seal the exterior cable entry, and secure mounting to avoid heat sources or direct sun causing false readings.

2. Repair/replace damaged cable or connectors: if external damage is found, the engineer will either repair junctions or replace the whole run. They will test continuity and resistance after repair.

3. Check boiler terminal block and harness: the engineer will isolate power, open the boiler, inspect the T1/T2 terminals and wiring harness, and measure the sensor input at the PCB to confirm the fault path. If wiring or connectors inside are corroded or loose they will be rectified.

4. Check for PCB or bus faults: if the sensor and wiring are good but the boiler still flags the error, the control PCB or controller bus could be at fault. This requires professional diagnostic equipment and possible component replacement.

5. Clear the fault and test operation: after repair the engineer will clear the fault code, run the boiler through heating cycles, verify the outdoor sensor readings are plausible, and confirm the boiler resumes correct weather-compensated operation. They will also check for any related fault codes.

When to call a professional: call a Gas Safe / licensed heating engineer if the fault persists after basic checks, if you find any damaged wiring, if the sensor needs replacing, or if the boiler shows additional internal fault codes. Do not attempt gas or internal electrical repairs yourself. A competent engineer will safely diagnose, replace parts if needed, and perform the required safety and performance checks to return the boiler to reliable operation.