Are you having problems with your Glow Worm boiler? If so, you’re not alone. Many homeowners and landlords experience issues with their Glow Worm boilers from time to time, and the best way to solve them is to understand the error codes.
This blog post will provide you with an overview of the most common Glow Worm boiler error codes and what the possible fault could be.
List of Glow-worm boiler error codes
| Boiler Model | Fault Codes | Cause of Problem |
| Betacom | Red LED On | Lockout – low water pressure (increase pressure to 1.5bar) and reset boiler |
| Betacom | Red LED flashing | Overheat – check both overheat stats |
| Betacom | Yellow LED flashing | Turn domestic hot water (DHW) control knob into temperature range and turn central heating (CH) temperature control knob into power (reset position) |
| Betacom | Yellow LED on | Flame present on the burner |
| Betacom | Green LED on | Green LED on |
| Betacom | Green LED off | No power to boiler – Check for 230volts into the appliance, check the fuse on printed circuit board (PCB) |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F00 / F10 / F71 | Flow heating temperature sensor fault |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F01 / F11 | Return heating temperature sensor fault |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F20 | Overheating fault |
| Betacom4 / Ultracom3 cxi / sxi / hxi / 35 / Flexicom cx / hx / sx | F9 / F22 | Low water pressure (or ignition temperature rise too slow) |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F26 / F77 | Fault in gas valve |
| Betacom4 / Ultracom3 cxi / sxi / 35 / CI / hxi / Xtramax HE | F27 / F16 | Flame detection fault |
| All Boilers | F28 / F1 / F4 | Ignition fault (flame detection) |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F29 | Loss of flame during operation |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F32 | Incorrect air pressure |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F49 | EBUS voltage fault |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F61 / F62 / F63 / F64 / F65 / F67 | Fault in the main board |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F68 | Fluctuation of flame signal |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F70 | User interface incompatible with the main board |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F72 / F84 | Permanent temperature difference between flow and return heating sensors |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F73 / F74 | Heating circuit pressure sensor fault |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F76 | Thermal fuse fault |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F83 | Thermal fuse fault |
| Betacom4 / Ultracom3 cxi / sxi / 35 | F85 | Flow and Return heating sensor fault |
| Betacom4/ Ultracom3 cxi / sxi / 35 | F86 | Underfloor heating contact fault |
| All Boilers | ERR / F12 / F18 | User interface fault |
| Betacom c | Temperature 30 flashing | Fault on central heating (CH) thermistor |
| Betacom c | Temperature 40 flashing | Fault on DHW thermistor |
| Betacom c | Temperature 50 flashing | Fault on outside sensor |
| Betacom c | Temperature 60 flashing | Low system pressure |
| Betacom c | Temperature 70 flashing | Fault on APS |
| Betacom c | Temperature 80 flashing | Overheat open circuit |
| Betacom c | Temperature 90 flashing | Flame or gas failure |
| Compact e / s | No DHW | Check dhw microswitch / Check external controls, Please test for 230V on switch live contact |
| Compact e / s | No C/H | Check dhw microswitch if dhw demand led is lit / Check external controls, Please test for 230V on switch live contact |
| Compact e / s | No C/H but boiler is firing | Check divertor motor and cartridge / Check external controls, Please test for 230V on switch live contact |
| Compact e / s | Boiler locks out within 10 seconds | Check pump proving switch, air pressure switch and overheat state / Check pump proving switch, air pressure switch and overheat stat |
| Compact e / s | Poor burner pressure | Check burner pressure/ignition adjustment pots on PCB |
| Ci Range (plus) / Si range | F2 | Fan/APS |
| All Boilers | F5 | Overheat Fault |
| All Boilers | F6 | Central heating flow thermistor |
| All Boilers | F7 | Domestic hot water thermistor |
| All Boilers | F8 | Tank thermistor fault |
| sxi / si / ci (plus) range / Xtramax HE | F9 | Water pressure sensor fault (please contact GW technical department for further information) |
| All boilers | F10 | Central return flow thermistor |
| All boilers | F11 | Main board connection fault |
| Ci (plus) / cxi / hxi / si / sxi range | F12 | Connection fault between main printed circuit board (PCB) and display PCB |
| Ci (plus) / cxi / hxi / si / sxi range | F13 | Main pcb connection fault |
| Ci (plus) / cxi / hxi / si / sxi range | F14 | Central heating flow temperature > 95 degrees |
| Ci (plus) / cxi / si / sxi range | F15 | Gas valve stepper motor fault |
| Ci (plus) / cxi / hxi / si / sxi range / Xtramax HE | F17 | Power supply is less than 170v |
| Ci (plus) / cxi / hxi / si / sxi range / Xtramax HE | F19 | Central heating thermistor unplugged |
| Ci (plus) / cxi / hxi / si / sxi range / Xtramax HE | F20 | Software incompatibility |
| cxi / hxi / sxi range / Flexicom cx | F24 | Central heating return temperature > 90 degrees |
| cxi / hxi / sxi / Xtrafast 96/120 / Xtrafast 96/120E1 | F25 / F26 / F11 | Poor circulation |
| ci range | F3 | Air fault |
| cxi / sxi / hxi range/ Xtramax HE | F2 / F3 | Fan |
| cxi / sxi range / Flexicom cx / hx / sx / hxi / Ultracom cxi / cx / hxi / sxi / Ultrapower sxi | F3 | Fan unable to reach ignition speed |
| Flexicom cx / hx / sx / hxi / Ultracom cxi / cx / hxi / sxi | F9 | Water pressure sensor fault, blocked flow filter or pump fault |
| Flexicom cx / hx / sx | F11 | Flow and or return thermistor fault |
| Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi / Xtramax HE | F13 | PCB memory or sensing fault |
| Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi / Xtramax HE | F14 | Gas valve control defective |
| Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi / Xtramax HE | F15 | E-bus voltage failure |
| All boilers | F25 / F23 | Circulation fault |
| Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi | F43 | Generic error |
| Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi | F70 | Software incompatible |
| Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi | F73 | Unable to see pump activate |
| Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi | F77 | Condensate pump error (optional) |
| hxi range | F9 | Earlier models only (please contact GW technical department for further information) |
| Ultracom? 35 Store | F02 / F12 | Hot water temperature sensor fault |
| Ultracom? 35 Store | F03 / F13 / F79 | Storage tank temperature sensor fault |
| Ultracom? 35 Store | F81 | Overheating of hot water circuit |
| All Ultracom | No display or Er | loose connection X51 |
| Xtramax HE Range | F24 | Cental heating return temperature > 90 degrees |
| Xtramax HE Range | F25 | Maximum temperature rise slope |
| Xtramax HE Range | F26 | Maximum delta temperature |
| Xtrafast 96/120 Range | F00 | No-fault |
| Xtrafast 96/120 Range / Xtrafast 96/120E1 Range | F00 | No-fault |
| Xtrafast 96/120 Range / Xtrafast 96/120E1 Range | F02 | Airflow fault |
| Xtrafast 96/120 Range / Xtrafast 96/120E1 Range | F05 | Overheating |
| Xtrafast 96/120 Range / Xtrafast 96/120E1 Range | F06 | Central heating thermistor/wiring fault |
| Xtrafast 96/120 Range / Xtrafast 96/120E1 Range | F08 | Storage vessel thermistor/wiring fault |
| Xtrafast 96/120 Range / Xtrafast 96/120E1 Range | F09 | System pressure sensor fault |
| Xtrafast 96/120 Range / Xtrafast 96/120E1 Range | F10 | Fan fault |
| Xtrafast 96/120 Range / Xtrafast 96/120E1 Range | F13 | Main printed circuit board (PCB) fault |
| Xtrafast 96/120 Range / Xtrafast 96/120E1 Range | F14 | Central heating flow temperature > 97 degrees |
| Xtrafast 96/120 Range / Xtrafast 96/120E1 Range | F15 | Gas mechanism fault |
| Xtrafast 96/120 Range / Xtrafast 96/120E1 Range | F20 | Communication fault |
Glow-worm Energy boiler range error codes
| Fault Code | Cause of Problem |
| F.00 | Flow temperature sensor |
| F.10 | Flow temperature sensor short circuit |
| F.12 and F.91 | Cylinder temperature sensor short circuit |
| F.13 | Domestic hot water cylinder temperature sensor short circuit |
| F.20 | Safety switch-off – overheating temperature reached |
| F.22 | Safety switch-off – low water pressure in the boiler |
| F.23 | Safety switch-off – temperature difference too great (NTC1/NTC2) |
| F.24 | Safety switch-off – temperature rise too fast |
| F.25 | Safety switch-off – flue gas temperature too high |
| F.27 | Safety switch-off – fault in flame detection |
| F.28 | Ignition unsuccessful when starting up |
| F.29 | Flame loss |
| F.32 | Fan frost protection function active – fan speed outside the tolerance values |
| F.33 | Fan frost protection function active – air pressure switch fault |
| FA9 | eBUS fault – voltage too low |
| F.61 | Gas valve control system fault |
| F.82 | Gas valve switch-off control fault |
| F.83 | EEPROM fault – electronics defective |
| F.64 | Electronics/sensor/analogue-to-digital converter fault |
| F.85 | Electronics temperature too high |
| F.67 | Value sent back by ASIC is incorrect (flame signal) |
| F.88 | Unstable flame (analogue input), underfloor heating contact or gas valve fault |
| F.70 | Invalid product code (DSN) |
| F.71 | Flow/return temperature sensor |
| F.72 | Deviation in the water pressure sensor/return temperature sensor |
| F.73 | Water pressure sensor not connected or has short-circuited |
| F.74 | Electrical problem in the water pressure sensor. For reliable electrical service, contact us for assistance! |
| F.75 | Pressure sensor fault |
| F.78 | The safety cut-out in the primary heat exchanger is defective |
| F.77 | Fault: Condensate or smoke |
| F.78 | Interruption to domestic hot water (DHW) outlet sensor at external controller |
| F.83 | Burner temperature sensor fault |
| F.84 | Flow/return temperature sensor fault |
| F.85 | Temperature sensor fault |
| F.87 | Electrodes fault |
| F.89 | Pump fault |
| Connection | No communication between the printed circuit board (PCB) and the user interface |
If you’re facing issues with your glow-worm boiler, our fault code guide is an excellent resource. Contact us for assistance! Our boiler repair expert will help diagnose the problem and provide effective solutions. We also offer emergency boiler repair services. With years of experience, we ensure your boiler runs efficiently and safely. Don’t hesitate to reach out!
