Error E53

Safety precautions:

- If you smell gas, or suspect a gas leak, do not operate electrical switches or the boiler. Turn off the gas at the meter if you can do so safely, open windows, evacuate the property and call the gas emergency number immediately.

- If anyone in the property has symptoms of carbon monoxide exposure (headaches, dizziness, nausea, flu-like symptoms that improve when you leave the building) evacuate and call emergency services and a Gas Safe engineer.

- Do not use naked flames, hairdryers on high heat, or boiling water on plastic condensate pipework. Do not attempt to dismantle the flue or boiler internals. Avoid unsafe ladder work; call a pro if the external terminal is hard to reach.

Initial checks a homeowner can do:

1. Turn the boiler off at the control panel, then turn off the electricity to the boiler at the isolator/switch on the wall before performing any external work (this is recommended by Baxi when thawing condensate).

2. Visually inspect the external flue terminal from ground level: look for obvious blockages such as birds’ nests, leaves, rubble or vegetation. Do not insert objects into the terminal.

3. Check other gas appliances: are they working? If none are working, ensure the gas supply is on (check the gas meter or supply valve) or check prepayment credit if applicable.

4. In freezing weather check the condensate pipe: the exposed section (usually outside or in an unheated area) can freeze and block, causing the boiler to lock out. If frozen, follow thawing steps below.

Specific diagnostic and fix steps you can try (safe, homeowner-level):

1. Thawing a frozen condensate pipe: with the boiler and its electricity turned off, locate the exposed condensate pipe. Warm it gently using a hot water bottle, a microwaveable heat pack, or warm (not boiling) water poured slowly from a watering can. Do not use a naked flame or boiling water. Once thawed, restore power and restart the boiler.

2. Restart/reset procedure: follow the boiler display/reset method in your user manual — typically a reset/standby button press or moving the selector to R and holding for a few seconds. Allow the boiler a few ignition attempts. Do not repeatedly try resetting the boiler more than a couple of times in a short period.

3. Clearing a simple external flue obstruction: if the flue terminal is safely reachable from ground level and the blockage is obvious (loose leaves, light debris), you may carefully remove the debris by hand or with suitable tools while the boiler is off. Do not push objects into the flue and do not attempt to dismantle the terminal cap. If clearance requires a ladder, working at height, or you are unsure, stop and call an engineer.

4. If the fault clears after thawing or clearing the flue, monitor the boiler for correct operation and unusual noises/smells. If it returns, or if the boiler runs but behaviour is abnormal, switch it off and call a Gas Safe engineer.

When to call a professional:

- If the boiler still shows E53 after the safe checks and a reset.

- If you cannot safely access or clear the flue terminal, or if the flue terminal appears damaged or blocked internally.

- If the fault appears to be caused by internal components (fan, burner, flue thermistor, PCB) or there is any sign of combustion smell, soot, yellow flame, or unusual behaviour.

- If you are not confident carrying out the safe checks described above.

A Gas Safe registered engineer should inspect and, if necessary, clean or replace the flue terminal, check combustion and CO levels, test and repair sensors or gas components, and carry out any required recalibration or safe repairs. Do not attempt internal repairs yourself. Keep the boiler off and the property ventilated if you suspect combustion or flue problems until a qualified engineer has confirmed it is safe to use.