The Baxi A.02.36 code means “Functional device disconnected.” The boiler expects a functional device within its configured control system but is no longer detecting it. Baxi’s public fault description does not name the device, connection or component involved, so the code should not be used to guess which part needs replacing.
Record the code exactly, note whether heating and hot water are affected, and find the complete boiler model. Keep the casing closed and do not unplug or reconnect controls. If A.02.36 remains or returns, arrange a professional repair.
What does Baxi A.02.36 mean?
Baxi lists A.02.36 as a functional device disconnected for its current Combi 2 and System 2 ranges. In homeowner terms, the control system is expecting an element that performs a function but cannot currently recognise its connection.
The wording is deliberately general. It does not tell you whether the message concerns a room control, sensor, accessory or an internal control element. It also does not prove that the device itself has failed. The connection, power, configuration or another part of the control arrangement may need to be checked by an engineer.
Which Baxi boilers can show A.02.36?
The current Baxi fault table applies the code to Baxi 200, 400, 600 and 800 Combi 2 boilers, Baxi Assure 500 Combi 2, Baxi 600 and 800 System 2, and Baxi Assure 500 System 2. Do not assume the same meaning for a different or older Baxi model.
Check your complete model name on the user guide, installation paperwork or an accessible external label. There is no reason to remove a boiler panel to find this information.
What is the disconnected functional device?
Baxi’s public code information does not identify it. That is an important safety boundary. Searching the code may produce confident claims about a particular thermostat, accessory or board, but those claims may not match your installation.
A qualified engineer can use the exact model, installed controls, code history and appropriate tests to establish what the boiler expected to detect. Until then, the accurate description is simply that an expected functional device is reported as disconnected.
What can you safely check?
Keep your checks outside the sealed appliance:
- Confirm that the display reads A.02.36, including the dots and leading zero.
- Photograph the code and any message that alternates with it.
- Record the full Baxi model name.
- Note whether heating, hot water or both have stopped.
- Check the visible status of ordinary room controls without changing settings beyond normal daily use.
- Note whether the message appeared after a power cut, service visit, installation or controls work.
If an external battery-powered control is blank, you can follow its own homeowner instructions. Do not pair, bypass, remove or rewire it merely because the boiler shows A.02.36.
Can you reset a Baxi A.02.36 code?
Try the normal reset once only if the official user guide for your exact model explains how. Reset arrangements vary across Baxi boilers. If the code stays on screen, returns or the boiler does not resume normal operation, stop resetting and book a repair.
Do not use factory-reset, installer, commissioning or configuration menus. They are not substitutes for finding why an expected device is no longer detected.
What should you avoid?
Do not open the boiler casing, test plugs or wiring, bridge terminals, inspect a control bus or replace a board or accessory. Do not disconnect other controls one by one to see whether the code changes. These actions can introduce new problems and erase useful clues.
A.02.36 alone is not evidence that a particular component must be bought. Correct repair work depends on the exact system and safe testing.
Is A.02.36 dangerous?
Baxi’s published meaning is a disconnected functional device, not a gas-leak or carbon-monoxide warning. However, do not bypass the error or keep restarting a boiler that behaves unusually.
If you smell gas, suspect carbon monoxide, feel unwell near the appliance or a carbon-monoxide alarm sounds, leave the property and follow current emergency guidance. Do not wait for a routine appointment.
Who should repair Baxi A.02.36?
A suitably qualified Gas Safe registered engineer should investigate a persistent A.02.36 code. They can confirm the model, identify the expected device safely and decide what work is required. A photograph of the display plus notes about recent work and the loss of heating or hot water can help.
Need the A.02.36 fault fixed?
Book a fixed-price boiler repair aimed at fixing the fault, with the booking price clear before the visit.
Quick answers about Baxi A.02.36
What does A.02.36 mean?
Baxi defines it as “Functional device disconnected.” The boiler is not detecting an expected device in its configured control arrangement.
Which device is disconnected?
The public Baxi description does not say. Do not assume it is a thermostat, sensor, accessory or control board.
Can I reconnect it myself?
No. Do not open the casing, disturb wiring or alter configured controls. A qualified engineer should identify the relevant device.
Should I reset the boiler?
One normal reset may be tried if the exact user guide instructs you. A returning code needs professional attention.
Does A.02.36 mean a part has failed?
Not necessarily. The code reports a disconnection but does not prove which device or connection is responsible.
What should I give the engineer?
Provide the exact code, full model, heating and hot-water status, other display messages and details of recent work or power interruptions.