Worcester Bosch 2945 fault codewhat it means and how to fix it
Too many short heat demands in a short time. The Greenstar 2000 has locked out because it kept being asked to fire and stop — usually a system with nowhere for the heat to go.
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What 2945 means
2945 is a locking fault on the Greenstar 2000 and the Worcester 2000 before it, and it is one of the few codes whose cause is the heating system's behaviour rather than a part failing. Worcester describe it as too many short heat demands in a short time period. A boiler that is asked for heat, fires, satisfies the demand in a minute or two and is asked again, repeatedly, is short cycling, and the 2000 counts the cycles and stops.
The remedy list is a picture of why it happens: reset the appliance with a factory reset, increase the restart blocking time, make sure that at least one thermostatic valve is open, check and replace a faulty heating pump, and check the diverter valve. The thermostatic valve line is the one that matters to a householder. On a small system where every radiator has a thermostatic valve and every one of them has closed, the boiler has no circuit to heat, its flow temperature shoots up, it stops, cools, and is called again — dozens of times an hour.
A radiator without a thermostatic valve, or one left open, is what the installation should have provided; Worcester's instruction is simply to make sure one is open. The pump and diverter valve entries are the same story from inside the boiler: if water does not move through the exchanger, every demand is satisfied instantly at the sensor and unsatisfied in the house. It is a nuisance code rather than a safety one, but it points at an installation issue that will keep coming back until it is addressed.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Every thermostatic radiator valve closed | Worcester's instruction is to make sure at least one is open. With none open the boiler heats a few litres of water, stops, and is called again within moments. | Common |
| Restart blocking time set too short | An installer setting. Worcester's remedy is to increase it so the boiler waits longer between demands. | Common |
| Pump not circulating | A failing pump has the same effect from the inside: the sensor is satisfied at once because the water is not moving. Worcester say check and replace. | Occasional |
| Diverter valve fault | Stuck between positions, it starves the heating circuit and produces the same rapid cycling. Last on Worcester's list. | Occasional |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£0–£450
Time on site
20 minutes
Free if a radiator valve is the answer. Installer setting change £70–£120. Pump £280–£450 if it has failed.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Central heating circulating pump
CH-PUMP-15-60£90–£180Plumbing merchant
Price checked 28 September 2026
Worcester Bosch Greenstar control board (PCB)
£250–£450Authorised Worcester parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Worcester Bosch fault codes
- E9 219Stop — call an engineerThe boiler has overheated and the safety thermostat has tripped. Water is not carrying heat away from the exchanger, and it should not be run until that is fixed.Related: overheat and circulation
- E9 224Stop — call an engineerOne of the two safety thermostats has tripped: the flue overheat thermostat or the high-limit stat on the heat exchanger. Worcester's own check list includes the burner gasket for flue gas leakage.Related: overheat and circulation
- A1 229Stop — call an engineerThe boiler has detected a dry-fire condition — it is trying to heat water that is not moving. Turn it off and leave it off until an engineer has seen it.Related: overheat and circulation
- E5 218Get it checkedThe flow temperature sensor has measured water leaving the heat exchanger far hotter than it should be. The boiler shut down to protect itself, and heat is not being carried away fast enough.Related: overheat and circulation
- E2 222Get it checkedThe flow temperature sensor is giving a reading the appliance cannot trust. Usually the sensor rather than the temperature.Related: overheat and circulation
- D1 240Get it checkedThe return temperature sensor has short circuited. The boiler has lost its reading of how warm the water is when it comes back from the radiators.Related: overheat and circulation
Own a Worcester Bosch boiler? Save it and its codes come first next time.
Related guides
Common questions about Worcester Bosch 2945
Why would a boiler complain about being asked for heat?
Because being asked and stopped dozens of times an hour wears the ignition components and does no heating. The 2000 counts the cycles and locks out so someone looks at why the demand keeps collapsing.
What is restart blocking time?
The minimum pause the boiler enforces between one heating demand ending and the next starting. It is an installer setting, and increasing it is Worcester's second remedy.
Does the 8000 Life have this code?
No. The 8000 Life, 8000 Style and 4000 tables do not include 2945; it is a Greenstar 2000 and Worcester 2000 code.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.