Worcester Bosch Greenstar Boilers
79 fault codes documented
1A4 E displayed — Temperature sensor in FW 100 defective
The display on the RT10 or FW 100 control unit shows '1A4 E'. This error indicates that the temperature sensor within the FW 100 unit is not working correctly.
1A8 E displayed — Bus communication error with TD 200 or heating appliance
The display on the RT10 or FW 100 control unit shows '1A8 E'. This indicates that the TD 200 or the main heating appliance, which communicate via the bus connection, are not responding.
2 pulses (blue light) — Flue pressure switch fault
The blue indicator light shows 2 pulses, signifying a fault with the flue pressure switch. This often means there's an issue with the flue's ability to clear combustion products.
5 pulses (blue light) — Volatile lockout (sensor, fan, or code plug issue)
The blue indicator light displays 5 pulses, indicating a volatile lockout related to a sensor, the fan, or the code plug. This is a general electronic fault.
A7 E displayed — General fault in the heating appliance
The display shows 'A7 E', which is an example of a general error from the main heating appliance. This code indicates a fault within the boiler itself, not specifically the control unit.
Blue light Fast flash — Hot water not working (central heating OK)
The blue indicator light flashes rapidly, indicating that the boiler is not producing hot water, although the central heating system is functioning normally. This points to an issue with hot water demand or supply.
Blue light Fast flash with 2 pulses — Boiler not responding to any demand
The blue indicator light performs a fast flash with two distinct pulses, meaning the boiler is failing to operate for both central heating and hot water demands. This indicates a general demand or control issue.
Blue light Fast flash with 5 pulses, Reset button Flashing — Ignition lockout
The blue indicator light flashes rapidly with five pulses, and the reset button is also flashing, indicating the boiler has entered an ignition lockout state. This means it tried to ignite multiple times and failed for safety reasons.
Blue light Off, Reset button Flashing — Internal boiler fault
The blue indicator light is off, but the reset button is flashing, indicating a general internal fault within the boiler's control system or major components that prevents operation.
Blue light Off, Reset button Off — No power to control board
The boiler's main blue indicator light and the reset button are both off, indicating a complete lack of power to the control board. This means the boiler cannot operate or respond.
Blue light Slow flash (off then on) — Central heating not working (hot water OK)
The blue indicator light flashes slowly (briefly turning on from an off state), and the central heating system is not operating, though hot water may still be available. This suggests an issue with central heating demand.
Blue light Slow flash (on then off) — Boiler running without central heating demand
The blue indicator light flashes slowly (briefly turning off from an on state), indicating the boiler is operating even when there is no active central heating demand from the external room thermostat or timer. This could lead to unnecessary heating.
Burner lights then goes out — Flue problem or combustion issue
The boiler's burner ignites successfully but then quickly extinguishes, failing to provide continuous heat for either hot water or central heating.
E9 and flashing reset button/fault LED — Safety temperature circuit tripped
The E9 code appears on the display, and both the reset button and the fault indicator LED flash. This indicates that the boiler's safety temperature circuit has activated, often due to overheating or low water pressure.
EA and flashing fault indicator LED — Flame not detected
The EA code is displayed, and the fault indicator LED is flashing. This indicates that the boiler's burner flame was not detected when it should have been.
F7 and flashing reset button/fault LED — Flame detected when appliance is off
The F7 code is displayed, and both the reset button and the fault indicator LED are flashing. This fault means that the boiler detects a flame even though the appliance has switched off, which is a safety concern.
Fast flash (blue) — Heat exchanger overheat
The boiler's blue indicator light flashes quickly, indicating that the heat exchanger has overheated. This is a critical safety shutdown.
Fault 01 Code 200 — BUS communication fault, boiler not reporting
The Worcester Bosch Greenstar CDi Boiler displays Fault 01 with code 200, indicating a communication issue on the BUS system where the boiler is no longer reporting its status to the controller.
Fault 01 Code 201 — BUS communication fault, incorrect device connected
The Worcester Bosch Greenstar CDi Boiler displays Fault 01 with code 201, indicating that an incorrect BUS subscriber device has been connected to the system, causing communication issues.
Fault 02 Code 40 — Internal fault, incorrect module type detected (FR110)
For the FR110 controller, the Worcester Bosch Greenstar CDi Boiler displays Fault 02 with code 40, indicating an internal fault where an incorrect module type has been detected in the system.
Fault 02 Code 42 — Internal fault, IPM code switch in intermediate position
The Worcester Bosch Greenstar CDi Boiler displays Fault 02 with code 42, indicating an internal fault where the code switch on the IPM (Intelligent Pump Module) is in an intermediate or incorrect position.
Fault 02 Code 43 — Internal fault, coding switch position changed
The Worcester Bosch Greenstar CDi Boiler displays Fault 02 with code 43, indicating an internal fault where the coding switch position has been changed since the initialisation phase.
Fault 02 Code 100 — Internal fault, ISM not responding
The Worcester Bosch Greenstar CDi Boiler displays Fault 02 with code 100, indicating an internal fault where the ISM (Internal System Module) is not responding to commands or communicating correctly.
Fault 02 Code 205 — Internal fault, parameters reset to default due to EEPROM problem
The Worcester Bosch Greenstar CDi Boiler displays Fault 02 with code 205, indicating an internal fault where some system parameters have reset to their factory default settings due to an EEPROM (Electrically Erasable Programmable Read-Only Memory) problem.
Fault 02 Code 255 — Internal fault, controller cannot control heating system
The Worcester Bosch Greenstar CDi Boiler displays Fault 02 with code 255, indicating a critical internal fault where the FW 100 or FR110 controller is no longer able to control the heating system.
Fault 03 Code 20 — Room temperature sensor faulty, circuit break
The Worcester Bosch Greenstar CDi Boiler displays Fault 03 with code 20, indicating a circuit break in the room temperature sensor built into the FW 100 or FR110 controller.
Fault 03 Code 21 — Room temperature sensor faulty, short circuit
The Worcester Bosch Greenstar CDi Boiler displays Fault 03 with code 21, indicating a short circuit in the room temperature sensor built into the FW 100 or FR110 controller.
Fault 11 Codes 131 or 132 — System configuration, new ISM detected
The Worcester Bosch Greenstar CDi Boiler displays Fault 11 with code 131 or 132, indicating that a new ISM (Internal System Module) has been detected within the system configuration.
Fault 12 — Cylinder High Limit Thermal Cut-out tripped
The Worcester Bosch Greenstar CDi Boiler controller displays Fault 12, indicating that the cylinder temperature has reached an excessively high level, causing the high limit thermal cut-out to trip as a safety measure.
Fault 12 Code 170 — System configuration, ISM1 not detected
The Worcester Bosch Greenstar CDi Boiler displays Fault 12 with code 170, indicating a system configuration issue where ISM1 (Internal System Module 1) is not detected by the controller.
Fault 12 Code 171 — System configuration, HLC tripped or ISM1 no longer detected
The Worcester Bosch Greenstar CDi Boiler displays Fault 12 with code 171, indicating that either the HLC (Hot Water Load Control) has tripped, or ISM1 is no longer detected despite being previously configured.
Fault 13 Code 157 — System configuration, BUS device changed or replaced (DHW)
The Worcester Bosch Greenstar CDi Boiler displays Fault 13 with code 157, indicating a system configuration issue where a BUS device related to the domestic hot water (DHW) system has been changed or replaced.
Fault 13 Codes 158 or 159 — System configuration, BUS device changed or replaced (heating circuit)
The Worcester Bosch Greenstar CDi Boiler displays Fault 13 with code 158 or 159, indicating a system configuration issue where a BUS device related to a heating circuit has been changed or replaced.
Fault 14 Code 117 — System configuration, incompatible BUS device (DHW for FR110)
For the FR110 controller, the Worcester Bosch Greenstar CDi Boiler displays Fault 14 with code 117, indicating an incompatible BUS device is present, especially if DHW is controlled by the boiler, making IPM control of DHW ineffective.
Fault 14 Codes 118 or 119 — System configuration, IPM for cylinder incorrect setting (FR110)
For the FR110 controller, the Worcester Bosch Greenstar CDi Boiler displays Fault 14 with code 118 or 119, indicating an incompatible BUS device due to the IPM for the cylinder not being set to identification 3 or higher.
Fault 15 Code 30 — Outside temperature sensor not connected or recognised
The Worcester Bosch Greenstar CDi Boiler displays Fault 15 with code 30, indicating that the outside temperature sensor is either not connected or not recognized by the system, making outside temperature data unavailable.
Fault 19 Code 202 — Unable to save parameter settings, BUS device unavailable
The Worcester Bosch Greenstar CDi Boiler displays Fault 19 with code 202, indicating that parameter settings cannot be saved because a configured BUS device is currently not available.
Fault 20 Code 193 — System configuration invalid, incorrect remote control coding
The Worcester Bosch Greenstar CDi Boiler displays Fault 20 with code 193, indicating an invalid system configuration due to incorrect coding in the remote control for the heating circuit. With FW 100, only coding 1 is possible.
Fault 29 Code 202 — Unable to save parameter settings, BUS device unavailable (remote control)
The Worcester Bosch Greenstar CDi Boiler displays Fault 29 with code 202, similar to Fault 19, indicating that parameter settings cannot be saved on the remote control because a configured BUS device is currently not available.
Fault 30 Code 7 — Mixer temperature sensor (MF) faulty
The Worcester Bosch Greenstar CDi Boiler displays Fault 30 with code 7, indicating that the mixer temperature sensor (MF) connected to the IPM is faulty.
Fault 33 Code 22 — Temperature sensors incorrectly connected (IUM)
The Worcester Bosch Greenstar CDi Boiler displays Fault 33 with code 22, indicating that a temperature sensor has been incorrectly connected to the IUM (Internal Unit Module) where it should not be.
Fault 40 Code 101 — Temperature sensor T1 faulty, short circuit
The Worcester Bosch Greenstar CDi Boiler displays Fault 40 with code 101, indicating a short circuit on the sensor lead for temperature sensor T1, which is on collector group 1.
Fault 40 Code 102 — Temperature sensor T1 faulty, break in sensor lead
The Worcester Bosch Greenstar CDi Boiler displays Fault 40 with code 102, indicating a break in the sensor lead for temperature sensor T1, which is on collector group 1.
Fault 41 Code 103 — Temperature sensor T2 faulty, short circuit
The Worcester Bosch Greenstar CDi Boiler displays Fault 41 with code 103, indicating a short circuit on the sensor lead for temperature sensor T2, located at the bottom of the solar cylinder.
Fault 41 Code 104 — Temperature sensor T2 faulty, break in sensor lead
The Worcester Bosch Greenstar CDi Boiler displays Fault 41 with code 104, indicating a break in the sensor lead for temperature sensor T2, located at the bottom of the solar cylinder.
Fault 50 Codes 121, 126, or 140 — Solar pump jammed or air in system
The Worcester Bosch Greenstar CDi Boiler displays Fault 50 with codes 121, 126, or 140, indicating that the solar pump is either physically jammed (sticking) or there is air present in the solar thermal system.
Fault 51 Codes 122, 123, 127, 132, or 133 — Incorrect temperature sensor type connected
The Worcester Bosch Greenstar CDi Boiler displays Fault 51 with codes such as 122, 123, 127, 132, or 133, indicating that an incorrect type of temperature sensor has been connected (e.g., a collector sensor used as a cylinder sensor, or PTC 1000 sensor used incorrectly).
Fault 52 Code 124 — Temperature sensors T1 and T2 reversed
The Worcester Bosch Greenstar CDi Boiler displays Fault 52 with code 124, indicating that temperature sensors T1 and T2 have been reversed or swapped in their connections.
Fault 53 Codes 125 or 128 — Temperature sensor T1 fitted in wrong location
The Worcester Bosch Greenstar CDi Boiler displays Fault 53 with code 125 or 128, indicating that the collector temperature sensor (T1) has been fitted in an incorrect location, specifically on the collector array inlet instead of the outlet.
Fault 54 Code 145 — Thermal disinfection temperature not reached or pump too low
The Worcester Bosch Greenstar CDi Boiler displays Fault 54 with code 145, indicating that the required temperature for thermal disinfection has not been reached in the solar cylinder, possibly due to a low maximum temperature setting or insufficient disinfection pump delivery rate.
Fault 55 Code 146 — Solar system not yet commissioned
The Worcester Bosch Greenstar CDi Boiler displays Fault 55 with code 146, indicating that the solar system has not yet been fully commissioned and is therefore not in operation.
Fault 56 Codes 147 or 154 — At least one pump/valve in manual mode
The Worcester Bosch Greenstar CDi Boiler displays Fault 56 with codes 147 or 154, indicating that at least one pump (e.g., solar pump SP or disinfection pump PE) or valve is currently set to manual mode instead of automatic.
Fault 59 - 201 — Mass flow rate in solar system too high
The display shows 'Fault 59' with a sub-code '201', indicating that the mass flow rate in the solar system for collector group 1 is too high.
Fault 59 - 202 — Mass flow rate in solar system too low
The display shows 'Fault 59' with a sub-code '202', indicating that the mass flow rate in the solar system for collector group 1 is too low.
Condensate pump: Flashing Green / Flashing Red — Dry-run detected
The Worcester Bosch Greenstar CDi Boiler's condensate pump lights flash green and red, indicating a dry-run condition, possibly due to air in the system. The pump should automatically restart after one minute.
Hot water temperature too high — Hot water is too hot
The hot water produced by the boiler is excessively hot, potentially posing a scalding risk and consuming more energy than necessary.
Hot water temperature too low — Hot water is not hot enough
The hot water produced by the boiler is not reaching the desired or expected temperature, making it unsuitable for use.
Incorrect or no control — Bus connection defective
The heating system is not being controlled correctly, or there is no control at all, indicating a communication problem with the devices on the bus.
Blue light on, but boiler not operating during demand — No heat or hot water
The blue indicator light is on, indicating power, but the boiler does not start heating when there is a demand for central heating or hot water.
Condensate pump: Off Green / Off Red — Mains power missing
The Worcester Bosch Greenstar CDi Boiler's condensate pump operating lights are both off, indicating that there is no mains power supplied to the pump.
No Central Heating but Hot Water OK — External control fault
The boiler provides hot water normally, but the central heating system does not turn on or heat up. This usually points to an issue outside the boiler itself.
No Hot Water or Central Heating demand — Boiler not receiving call for heat
Neither hot water nor central heating is being produced, and the boiler is not responding to any calls for heat. This indicates the boiler isn't receiving a signal to operate.
No Hot Water but Central Heating OK — External control fault
The boiler heats the central heating radiators normally, but no hot water is available for taps or showers. This typically indicates a problem with external components.
No light — No power to boiler
The blue central indicator light is off, meaning there is no electrical power reaching the boiler or its control components.
No on/off indicator light — Boiler appears off or unresponsive
The blue on/off indicator light is not illuminated, and the boiler appears to be off or not receiving a signal to operate, even if mains power is seemingly present.
Boiler noisy or going to overheat — Circulation or pump issue
The boiler makes excessive noise or frequently reaches an overheat condition, indicating a problem with water circulation or the pump.
Condensate pump: Off Green / Flashing Red — Pump blocked and alarm level exceeded
The Worcester Bosch Greenstar CDi Boiler's condensate pump shows no green light but a flashing red light, indicating that the pump is blocked and the condensate level has also exceeded the alarm level.
Condensate pump: On Green / Flashing Red — Pump blocked
The Worcester Bosch Greenstar CDi Boiler's condensate pump shows a steady green light and a flashing red light, indicating that the pump is blocked.
Condensate pump: On Green / On Red — Level exceeds alarm level
The Worcester Bosch Greenstar CDi Boiler's condensate pump shows a steady green light and a steady red light, indicating that the condensate level has exceeded the alarm level.
Required temperature not reached
The room or heating system is not reaching the desired temperature setting, indicating an issue with heat delivery.
Reset button and fault indicator LED flashing — Appliance locked (Category 4 fault)
For Category 4 faults on the Worcester Bosch Greenstar CDi Boiler, the appliance is disabled and locked. This is indicated by both the 'reset' button and the fault indicator LED flashing simultaneously.
Required room temperature is greatly exceeded
The room temperature is significantly higher than the desired setting, leading to uncomfortable overheating.
Excessive room temperature fluctuations
The room temperature varies significantly, rising and falling beyond comfortable levels, even with the heating system active.
Room temperature too high in low mode
Even when the heating system is operating in a reduced or 'low mode,' the room temperature remains higher than expected.
Desired room temperature not reached — Heating is insufficient
The central heating system is on, but the room does not reach the temperature set on the thermostat or programmer, resulting in a colder environment than desired.
Desired room temperature exceeded — Heating is too strong
The room temperature is significantly higher than the temperature set on the thermostat, leading to overheating and discomfort.
Slow flash (blue, normally off, flashes on) — Ignition lockout
The boiler's blue indicator light flashes slowly from off to on, indicating an ignition lockout. This means the boiler failed to ignite the gas.
Slow flash (blue, normally on, flashes off) — Flue overheat
The boiler's blue indicator light flashes slowly from on to off, signaling that the flue temperature is too high. This is a safety measure to prevent damage.
Temperature rise instead of fall
The temperature is increasing when it should be decreasing according to the schedule or settings.