Glow-worm Boiler Fault Codes: A Complete Guide
If your Glow-worm boiler displays an error message, understanding the fault code can help you diagnose the problem more quickly and reduce stress while waiting for a Gas Safe engineer.
This guide provides a complete list of Glow-worm boiler fault codes across all models, including combi, system, and regular heat-only boilers. Whether your boiler shows an F1, F22, or another error code, this article is designed to help you understand what it means and what steps to take next.
About Glow-worm Boilers
Glow-worm is a well-established British boiler manufacturer with over 80 years of experience in the heating industry. The company began manufacturing boilers in 1934 at the Derwent Foundry in Derbyshire. Since 2001, Glow-worm has been part of the Vaillant Group, Europe’s second-largest heating technology company.
Glow-worm boilers are designed for efficiency, reliability, and affordability. Their range includes options for various home sizes and heating needs, from compact combi boilers to high-output system models.
Are Glow-worm Boilers Reliable?
In a Which? Best Boiler Brands survey, Glow-worm received an overall brand score of 57%, placing 7th out of 13 boiler manufacturers. This rating was based on feedback from over 7,500 boiler owners and 153 Which? Trusted Trader engineers, who rated brands across key criteria such as:
- Reliability
- Customer satisfaction
- Engineer recommendations
- Build quality
- Availability of parts and spares
- Ease of servicing and repair
Notably, Glow-worm received 4.3 out of 5 stars for customer satisfaction, indicating that many users still have a positive experience with the brand despite it not ranking at the very top.
Glow-worm Boiler Error & Fault Codes
Below is a complete list of common Glow-worm boiler fault codes to help you understand what might be wrong with your boiler. While this guide is helpful for initial troubleshooting, a qualified Gas Safe registered engineer must handle any boiler issues.
| Boiler Model | Fault Codes | Cause of Problem |
|---|---|---|
| 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 |
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 |
| 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 |
Glow-worm Error Codes F1, F4, F28 or F29
If you are seeing the error codes F1, F4 F28, or F29 on your boiler there’s an issue with your condensate pipe. This error appears when your pipe is frozen, which can happen during the cold months as it runs outdoors. You can fix this issue yourself if you feel confident enough, otherwise call an engineer, by thawing out the pipe which you can find out how to do with our handy guide to thawing a condensate pipe.
Glow-worm Boiler Manuals
- Glow worm 23 C
- Glow worm 24 CI
- Glow worm 18 SI
- Glow worm 24CXi
- Glow worm 30CXi
- Glow worm 38CXi
- Glow worm 30Ci
- Glow worm BBU 45/4
- Glow worm BBU 54/4
- Glow worm BBU 45/2
- Glow worm BBU 56/2
- Glow worm Betacom 24a
- Glow worm Betacom 28a
- Glow worm Betacom 24c
- Glow worm Betacom 2 24
- Glow worm Betacom 2 28
- Glow worm Betacom 3 24c-A (H-GB)
- Glow worm Betacom 3 30c-A (H-GB)
- Glow worm Betacom 4 24c-A
- Glow worm Betacom 4 30c-A
- Glow worm Black beauty
- Glow worm Capricorn gas fire front
- Glow worm Capricorn 240 boiler
- Glow worm Capricorn 246 boiler
- Glow worm Compact 100e
- Glow worm Easicom 24
- Glow worm Easicom 28
- Glow worm Easicom 3 24C
- Glow worm Easicom 3 28C
- Glow worm Energy 12S
- Glow worm Energy 15S
- Glow worm Energy 18S
- Glow worm Energy 25S
- Glow worm Energy 30S
- Glow worm Energy 25c
- Glow worm Energy 30c
- Glow worm Energy 35c
- Glow worm Energy saver 40
- Glow worm Energy saver 60
- Glow Worm Energy saver 50e
- Glow Worm Energy saver 60e
- Glow worm Energy 35 Store-A (H-GB)
- Glow worm Energy 2 30C LPG
- Glow worm Flexicom 24 CX
- Glow worm Flexicom 30 CX
- Glow worm Flexicom 35 CX
- Glow worm Flexicom 12hx
- Glow worm Flexicom 15hx
- Glow worm Flexicom 18hx
- Glow worm Flexicom 24hx
- Glow worm Flexicom 30hx
- Glow worm Flexicom 35hx
- Glow worm Flexicom 18SX
- Glow worm Flexicom 30SX
- Glow worm Galaxie 246
- Glow worm Galaxie 246N
- Glow worm Hideaway 40 B
- Glow worm Hideaway 40
- Glow worm Hideaway 50B
- Glow worm Hideaway 50
- Glow worm Hideaway 60B
- Glow worm Hideaway 60
- Glow worm Hideaway 70B
- Glow worm Hideaway 70
- Glow worm Hideaway 80B
- Glow worm Hideaway 80B FF
- Glow worm Hideaway 80
- Glow worm Hideaway 80C FF
- Glow worm Hideaway 100B
- Glow worm Hideaway 100
- Glow worm Hideaway 120B
- Glow worm Hideaway 120
- Glow worm 12hxi
- Glow worm 15hxi
- Glow worm 18hxi
- Glow worm 24hxi
- Glow worm 30hxi
- Glow worm 38hxi
- Glow worm Icon 23T
- Glow worm Icon 28T
- Glow worm Icon 40-50 ci
- Glow worm Inset BBU40
- Glow worm Inset BBU50
- Glow worm Jaguar combi 23Kw
- Glow worm Jaguar combi 28Kw
- Glow worm Micron 30FF
- Glow worm Micron 40FF
- Glow worm Micron 50FF
- Glow worm Micron 60FF
- Glow worm Micron 70FF
- Glow worm Micron 80FF
- Glow worm Micron 100FF
- Glow worm Micron 120FF
- Glow worm Space Saver 50 Mk11
- Glow worm Space Saver 30B
- Glow worm Space Saver 60B
- Glow worm Space Saver 20-30F
- Glow worm Space Saver 30-40F
- Glow worm Space Saver 40-50F
- Glow worm Space Saver 50-60F
- Glow worm Space Saver 45-60
- Glow worm Space Saver 65-75F
- Glow worm Space Saver Complheat 30
- Glow worm Space Saver Complheat 40
- Glow worm Space Saver Complheat 50
- Glow worm Space Saver KFB 30
- Glow worm Space Saver KFB 40
- Glow worm Space Saver KFB 50
- Glow worm Standalone
- Glow worm 18sxi
- Glow worm 30sxi
- Glow worm Ultimate 30C
- Glow worm Ultimate 35 C
- Glow worm Ultimate 30BF
- Glow worm Ultimate 30FF
- Glow worm Ultimate 40BF
- Glow worm Ultimate 40CF
- Glow worm Ultimate 40FF
- Glow worm Ultimate 50BF
- Glow worm Ultimate 50CF
- Glow worm Ultimate 50FF
- Glow worm Ultimate 60BF
- Glow worm Ultimate 60CF
- Glow worm Ultimate 60FF
- Glow worm Ultimate 70FF
- Glow worm Ultimate 80FF
- Glow worm Ultimate 70FF
- Glow worm Ultimate 80FF
- Glow worm Ultimate 100FF
- Glow worm Ultimate 120FF
- Glow worm Ultimate 3 30C
- Glow worm Ultimate 3 35C
- Glow worm Ultimate 3 25r-A (H-GB)
- Glow worm Ultimate 3 25s
- Glow worm Ultracom 24cx
- Glow worm Ultracom 30cx
- Glow worm Ultracom 24cxi
- Glow worm Ultracom 30cxi
- Glow worm Ultracom 38cxi
- Glow worm Ultracom 18sxi
- Glow worm Ultracom 30sxi
- Glow worm Ultracom2 24cxi
- Glow worm Ultracom2 30cxi
- Glow worm Ultracom2 35cxi
- Glow worm Ultracom2 12sxi
- Glow worm Ultracom2 18sxi
- Glow worm Ultracom2 30sxi
- Glow worm Ultrapower 100sxi
- Glow worm Ultrapower 170sxi
- Glow worm Xtrafast 96
- Glow worm Xtrafast 120
- Glow worm Xtramax
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