Overview
E9 219 on a Worcester Bosch GB162 means the boiler's safety temperature detection has recorded an internal temperature above about 105°C and the boiler has locked out. This is a deliberate safety action: the safety temperature limiter (or associated sensor) trips to prevent damage to the heat exchanger and other components when the water/flow temperature becomes dangerously high. This fault is potentially serious. Common causes are poor circulation (blocked or seized pump, closed valves, airlocks), a heat exchanger problem (limescale or partial blockage causing local overheating), a failed temperature sensor or high-limit thermostat, or an electronic/PCB fault giving incorrect readings. Some basic checks (reset, system pressure, radiator bleeding, ensuring valves are open) are safe for a homeowner, but if the fault returns, if you see leaks, steam, or smell gas, or if you are not confident, this requires a Gas Safe registered engineer. Do not attempt internal repairs, replace sensors, or work on gas/electrical components yourself.
Possible Cause: The safety temperature sensor has captured a temperature in excess of 105°C.
Troubleshooting Steps
Safety first:
- If you smell gas, evacuate the property and call your gas emergency number immediately. Do not operate electrical switches.
- If the boiler or pipes are very hot or steaming, switch the boiler off at the programmer and the isolator/power switch and allow it to cool. Do not open the boiler casing.
- Do not repeatedly reset the boiler more than 2 times; repeated resets can cause further damage.
Initial homeowner checks (safe, non-intrusive):
1) Note down the exact error code (E9 219) and the time it occurred. This information is useful for the engineer.
2) Reset the boiler once using the manufacturer reset method: turn the mode selector to the reset position (or OFF, wait 30 seconds, then back to heating) and see if it restarts. If it restarts, observe operation but still investigate root cause—do not assume problem is fixed if it returns.
3) Check system pressure on the boiler gauge. Target pressure is about 1.0–1.5 bar when cold. If pressure is low, top up using the filling loop following the boiler's instructions. Low pressure can cause circulation problems.
4) Check radiators: ensure radiator valves and TRVs are open. Feel the flow and return pipework on the boiler and the first radiator close to the boiler (when safe) after starting heating—if the flow pipe is hot but return is cold or radiators are cold at the top, circulation may be blocked or pump may not be working.
5) Bleed radiators to remove trapped air which can cause poor circulation and overheating in the boiler.
6) Listen to the boiler while it tries to run: a working pump usually hums or vibrates. If you hear nothing when the boiler should be circulating, or you hear loud banging/rumbling, it suggests a pump or circulation problem.
7) Inspect around the boiler for visible leaks, steam, or signs of water ingress. If present, switch the boiler off and call an engineer.
Specific diagnostic steps and what they indicate (for information; do not open the boiler):
- If resetting clears the fault but it returns quickly, this suggests an active circulation or heat build-up problem (pump, closed valves, blocked system, or blocked heat exchanger).
- If the pump appears dead (no hum/vibration) or radiators remain cold, a seized or failed pump is likely; this requires engineer intervention.
- If the pressure repeatedly drops or is very low, there may be a leak in the system causing flow problems.
- If the fault includes cause code 219 noted by the boiler, this commonly points toward heat exchanger issues (blockage, limescale) or associated high temperatures in the exchanger area.
Practical do-it-yourself actions you can safely try:
- Perform the single reset as described and watch for immediate reappearance of the fault.
- Top up system pressure if it is low following the boiler instructions and re-check operation.
- Bleed radiators to remove airlocks and improve circulation.
- Ensure all radiators and zone valves are open and any isolation valves near the boiler are not closed.
- Thaw condensate pipe only if you are sure the fault relates to a frozen condensate (more common in EA/229 faults), and only by pouring warm (not boiling) water on the external pipe; do not force or heat with a flame.
When to call a professional (Gas Safe engineer):
- Any time the E9 219 fault returns after a single reset.
- If you suspect a blocked/seized pump, blocked heat exchanger, sensor failure, or PCB/electronics fault.
- If you find leaks, steam, signs of overheating, or smell gas.
- If you are uncomfortable performing the simple checks above.
What the engineer will typically check and may do:
- Read and log the boiler fault codes and live temperature readings.
- Check circulation: pump operation, isolating valves, flow/return temperatures, and radiator flow.
- Inspect the safety temperature sensor/limiter and wiring for failure or water damage.
- Inspect the heat exchanger for limescale, blockages, or faults and consider descaling or replacement if required.
- Check the PCB and other control electronics if sensor signals are inconsistent.
- Perform a system flush if sludge or scale is causing poor flow, or recommend targeted repairs (pump replacement, sensor replacement, heat exchanger repair/replacement).
Final points:
- E9 219 indicates an over-temperature safety event; don’t ignore it. Leaving the boiler to run while overheating risks further damage.
- Do not attempt internal repairs or work on gas/electrical parts unless you are a Gas Safe qualified engineer. Arrange a visit from a Gas Safe registered heating engineer if the fault persists after the basic checks or if you observe any unsafe signs.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Worcester Bosch GB162 Boiler.