Which faults are most common on Worcester Bosch boilers?
Worcester Bosch is one of the most common boiler makes in UK homes, and its Greenstar combis and system boilers are fitted widely across Birmingham. Most of the faults owners report fall into a few groups.
Ignition lockouts (EA). The boiler tries to light, cannot detect a flame, and locks out. Worcester’s manual lists gas pressure, the flue, the ignition parts and blocked condensate pipes among the checks. In a cold snap, a frozen condensate pipe is one of the most frequent causes, and you can often clear it yourself with warm water. See our frozen condensate pipe guide.
Overheat lockouts (E9). When water is not moving through the boiler properly, it gets too hot and a safety thermostat shuts it down. Low pressure, air, sludge and pump faults are the usual culprits. Our E9 guide explains the checks.
Pressure loss. A sealed system that keeps dropping below 1 bar points to a leak or a tired expansion vessel. See boiler losing pressure.
Diverter valve faults on combis. Heating but no hot water, or the reverse, often comes down to the diverter valve on older Greenstar combis.
Servicing a Worcester Bosch boiler
An annual service checks combustion, the flue, the seals, the electrodes and the condensate trap, which covers several of the causes of an EA lockout before they strike. Keep the service record with the boiler’s paperwork, as Worcester guarantees usually depend on it. See boiler servicing for what a service includes.
Under guarantee, or out of guarantee?
If your Worcester boiler might still be within its guarantee, contact Worcester Bosch first. Repairs by someone else can affect a manufacturer guarantee, and many faults will be put right at no charge. Once the guarantee has ended, send us an enquiry and we arrange a local Gas Safe registered engineer who will diagnose the fault and give you a price before any work starts.
When should you get an engineer?
Reset a Worcester boiler once, after checking the gas, the condensate pipe and the pressure. If the code returns, the cause is inside the boiler: an electrode, a fan, a sensor, a pump or the gas valve. Those are jobs for a Gas Safe registered engineer. Fan codes such as C6 are never a homeowner fix. When you send an enquiry, include the model name from the front of the boiler and both parts of the code.