Baxi E135 fault code explained

The Baxi E135 fault code means internal error. That is the exact description in Baxi’s current error-code table for the affected combi and system boiler group.

“Internal error” is deliberately broad. It tells an engineer that the appliance controls have detected an internal condition they cannot accept, but it does not identify one guaranteed failed part. Keep the casing closed and arrange proper diagnosis if the code remains.

What does Baxi E135 mean?

Baxi lists E135 as “Internal error”. Unlike a code that names low pressure or a fan fault, E135 does not give the homeowner a specific external cause to correct.

The code should therefore not be translated into an invented component failure. An engineer must use the exact model literature and test results to establish what the boiler has detected.

Which Baxi boilers can show E135?

Baxi places E135 in the error-code group covering these combi and system families:

• Baxi Platinum Compact Combi;
• Baxi Duo-tec Compact Combi;
• Baxi Megaflo Compact System;
• Baxi 600 Combi and System;
• Baxi 800 Combi and System;
• Baxi Duo-tec Combi;
• Baxi Assure Combi and System;
• Baxi Platinum Combi and Platinum+ Combi;
• Baxi Megaflo System;
• Baxi EcoBlue Combi and System.

The same manufacturer table groups some Main and Potterton products, but this article concerns boilers carrying the Baxi name. Confirm the label and user guide because range names and control versions vary.

What might you notice?

The boiler may lock out, stop heating, stop producing hot water or show the code intermittently. A temporary restart does not prove the underlying condition has disappeared.

Record whether the display says E135 continuously or alternates characters, and whether another code appeared before or afterwards.

Can I reset E135?

Baxi’s homeowner reset guide explains that models use different controls: a dedicated reset button, selector switch or temperature-control position. Follow only the procedure for your exact boiler.

One correct reset is reasonable if there is no smell of gas, no carbon-monoxide alarm, no scorching, no leak reaching electrics and the user guide permits it. If E135 returns, stop resetting and contact Baxi under warranty or a Gas Safe registered engineer.

Safe checks before booking

• Photograph the closed boiler and display.
• Find the exact model and serial number from accessible documents, a pull-out tag or label.
• Note whether heating, hot water or both are affected.
• Record any recent power interruption, service or repair.
• Check the warranty status.
• Make the boiler safely accessible.

Do not remove the front panel, unplug internal leads, alter control-board settings or buy a replacement part from the code alone. Baxi reserves installer repair actions for its professional technical system.

Is E135 a low-pressure fault?

No. In the affected Baxi code group, low water pressure is E118, while E135 is internal error. Topping up the heating circuit solely because E135 is displayed is not supported by the manufacturer’s code meaning.

Is it a gas-supply fault?

Baxi uses other codes for gas-supply, ignition and flame problems. E135 remains listed only as internal error. Do not assume there is a gas-supply problem unless there is separate evidence.

If you smell gas, leave the property, avoid switches and naked flames, and call the National Gas Emergency Service on 0800 111 999.

What will an engineer do?

The engineer will identify the exact model, read any available fault history, check the appliance against the correct Baxi documentation and test the relevant controls safely. The results determine whether the problem is configuration, wiring, a control component or another internal condition.

An online list of speculative parts is not a diagnosis and can waste money. E135 must be assessed on the actual appliance.

The short answer

Baxi E135 means internal error. It applies to the Baxi model group listed by the manufacturer, but it does not name one certain failed component. Follow the exact user reset procedure once; if the code returns, keep the casing closed and arrange qualified diagnosis.