Heatline Boiler Error Codes / Fault Codes List
If your Heatline boiler has stopped working or shows an error code, you’re in the right place. This guide includes a full list of Heatline boiler fault codes, links to user manuals and installation instructions for various models.
Heatline is a long-established name in the UK boiler market and is now part of the Vaillant Group. Known as a budget-friendly option, Heatline boilers are typically compact, condensing combi boilers designed to provide affordable heating and hot water solutions. While they may not always receive the highest praise from heating engineers, many households rely on them for everyday use.
If you’re experiencing problems with your boiler, don’t worry — even the most reliable boiler brands can encounter faults over time. This page will help you identify what the fault code on your Heatline boiler means, giving you a better understanding of what might be wrong and what steps to take next.
Important: Always consult a qualified Gas Safe engineer for any boiler repairs. This guide is designed to help you better understand the issue, estimate potential repair costs, and decide whether a replacement boiler might be more cost-effective in the long run.
If your Heatline boiler is out of warranty and repair costs are stacking up, it may be worth considering a new, energy-efficient boiler. WarmZilla offers competitive pricing, flexible boiler finance options, and installations that include everything you need to get back up and running with peace of mind.
Check the table below for your Heatline boiler error code and see what it means.
| Fault Code | Description | Cause | Solution |
|---|---|---|---|
| F00 | Flow heating temperature sensor fault | Sensor open circuit | • Check the sensor’s connections • Check the wiring harness • Check the sensor |
| F01 | Return heating temperature sensor fault | Return heating temperature sensor disconnected | • Check the sensor’s connections • Check the wiring harness • Check the sensor |
| F10 | Flow heating temperature sensor fault | Sensor short-circuit | • Check the sensor’s connections • Check the wiring harness • Check the sensor |
| F11 | Return heating temperature sensor fault | Return heating temperature sensor shorted | • Check the sensor’s connections • Check the wiring harness • Check the sensor |
| F20 | Overheating fault | Overheating safety device activated (97°C) | • Check the operation of the pump • Check the wiring harness • Ensure flow and return valves are open |
| F22 | Low water pressure (<0.3 bar) | Closed valve / Pump disconnected / Leak in installation | • Fill and purge the system • Check pump and sensor connections • Inspect for leaks |
| F23 | High temperature difference between flow and return | Water circulation fault | • Check the flow and return heating sensor connection • Check pump speed |
| F24 | Water circulation fault | Pump malfunction (rapid temp increase) | • Ensure isolation valves are open |
| F26 | Gas valve motor fault | Disconnected or defective cables | • Check valve and condensate pump connections • Check the operation of the gas valve • Check the operation of the condensate pump |
| F27 | Flame detection fault | Abnormal flame signal | • Check the flame detection electrode, igniter unit, and main board |
| F28 | Ignition fault | No/insufficient gas flow, faulty electrode or igniter | No return gas / Insufficient gas flow Gas valve incorrectly adjusted Defective firing electrode and flame control / Defective igniter unit |
| F29 | Flame loss during operation | No/insufficient gas flow, faulty electrode or igniter | No return gas / Insufficient gas flow Gas valve incorrectly adjusted Defective firing electrode and flame control / Defective igniter unit |
| F32 | Incorrect air pressure | Incorrect fan speed | • Check flue system and fan connections |
| F49 | EBUS voltage fault | Fault in EBUS line short circuit in EBUS connector | • Check eBus control wiring |
| F61 | Main board fault | Gas valve command fault | • Check the main boards connections. • Check the main board. • Check the appliance DSN number is correct. • Reset the appliance. |
| F62 | Gas valve closure fault | Gas valve command fault | • Check the main boards connections. • Check the main board. • Check the appliance DSN number is correct. • Reset the appliance. |
| F63 | Main board memory fault | Fault in main board | • Check the main boards connections. • Check the main board. • Check the appliance DSN number is correct. • Reset the appliance. |
| F64 | Fault in main board | Rapid fluctuation of return or flow heating sensor | • Check the main boards connections. • Check the main board. • Check the appliance DSN number is correct. • Reset the appliance. |
| F65 | Fault in main board | Excessive main board temperature | • Check the main boards connections. • Check the main board. • Check the appliance DSN number is correct. • Reset the appliance. |
| F67 | Fault in main board | Flame signal fault in main board | • Check the main boards connections. • Check the main board. • Check the appliance DSN number is correct. • Reset the appliance. |
| F68 | Flame signal fluctuation | Incorrect gas flow / Ignition issue | • Check the return gas circuit (gas valve open). • Check the observe the fl ame picture and check the CO2 setting. • Check the igniter unit connections. • Check the state of the electrode (corrosion). |
| F70 | User interface incompatible with main board | Incorrect product code | • Check that the appliance DSN code on the screen matches the product code of the nameplate (in the event of a fault and the appliance DSN does not appear). • Check the board’s reference. |
| F71 | Flow heating temperature sensor fault | Flow heating temperature sensor unclipped or defective (no temperature variation) | • Check sensor and ensure it’s clipped |
| F72 | Permanent temperature difference between flow and return heating sensors. | Mismatch between the flow and return heating temperatures (permanent difference) | • Check and replace faulty sensors |
| F73 | Heating circuit pressure sensor fault | Sensor shorted/disconnected | • Check the sensor’s connections • Check the sensor |
| F74 | Heating circuit pressure sensor fault | Fault in pressure sensor | • Check the sensor’s connections • Check the sensor |
| F76 | Thermal fuse fault | Disconnected or defective fuse | • Check fuse • Replace heat exchanger |
| F77 | Gas valve motor issue | Defective gas valve. Defective condensate pump (option) | • Check the gas valve connections. • Check the operation of the gas valve. • Check the operation of the condensate pump (option). |
| F83 | No water in the installation: the temperature does not increase when the burner is lit | Closed valve / Leak / Pump issue | • Fill the installation. • Purge the installation. • Check the pump connections. • Check the flow and return heating sensor connections. • Check that there are no leaks |
| F84 | Permanent temp difference | Inverted or disconnected flow and return heating temperature sensors Defective temperature sensors | • Check sensor connections and replace if needed |
| F85 | Flow and return heating sensors fault | Flow and return heating temperature sensor connected to same tube | • Check temperature sensors connections |
| F86 | Underfloor heating contact fault | Floor heating contact open Sensor disconnected or defective | • Check sensor and connections |
| Err | User interface fault | Defective user interface | • Check interface PCB and wiring • Replace if needed |
Below is a complete list of Heatline boiler manuals courtesy of our friends over at
- freeboilermanuals.com
- Heatline Capriz 25kW Boiler Manual
- Heatline Capriz 28kW Boiler Manual
- Heatline Capriz 25S Boiler Manual
- Heatline Capriz 28S Boiler Manual
- Heatline Capriz Plus 24kW Boiler Manual
- Heatline Capriz Plus 28kW Boiler Manual
- Heatline Capriz 2 24C Boiler Manual
- Heatline Capriz 2 28C Boiler Manual
- Heatline Compact S20S Boiler Manual
- Heatline Compact S24S Boiler Manual
- Heatline Compact S30S Boiler Manual
- Heatline C24kW Boiler Manual
- Heatline C28kW Boiler Manual
- Heatline Monza 24kW Boiler Manual
- Heatline Monza 28kW Boiler Manual
- Heatline Sargon 24kW Boiler Manual
- Heatline Sargon 30kW Boiler Manual
- Heatline Sargon 35kW Boiler Manual
- Heatline Solaris 24PC Boiler Manual
- Heatline Solaris 30PC Boiler Manual
- Heatline Vizo 24kW Boiler Manual
- Heatline Vizo 28kW Boiler Manual
- Heatline Vizo Plus 24kW Boiler Manual
- Heatline S24kW Boiler Manual
- Heatline S30kW Boiler Manual
If you have any questions about your error code then we’re always here to help or advise. Just get in touch with us using our live chat or by emailing ask@warmzilla.co.uk
Did you enjoy?
Have a question? Please contact us on Live Chat
About the Author
What does a flashing + sign mean on a heatline Capriz 28c boiler indicate?
Thanks Jan, flashing lights can indicate a variety of issues. For guidance, take a look at our fault code blog, where you’ll also find manuals at the bottom of the page. If you have any questions, our team will be happy to help.
https://www.warmzilla.co.uk/blog/heatline-boiler-error-codes-fault-codes-list