Error E135

Safety precautions:

- If you smell gas, leave the property immediately, do not operate electrical switches, and contact the emergency gas number. Do not attempt any repairs yourself.

- Only a Gas Safe registered engineer should work on gas appliances, gas valves, the burner or the PCB. Do not remove covers that expose live parts or gas components unless you are qualified.

- Before doing any simple checks, turn off the boiler electrical supply at the isolator if you are going to inspect pipes or external connections. Never open the boiler casing unless instructed by a qualified engineer.

Initial homeowner checks you can safely do:

1. Note the exact error code and any other text or symbols on the display and take a photo. Record the boiler model and serial number.

2. Try a controlled reset: on GA-range boilers either press and hold the reset/standby button for 1–3 seconds or turn the selector to the R (reset) position and hold for about 5 seconds, then return to normal. If you are trying to relight for hot water, turn on a hot tap while you reset so the boiler registers demand (you should see a flashing tap symbol then a flame symbol if successful).

3. Check mains power: ensure the boiler is powered (fuse, isolator, RCD not tripped). Replace any dead thermostat batteries and check room/stat settings.

4. Check basic external causes that sometimes cause ignition/operation faults: confirm your gas supply is on (check other gas appliances), ensure the gas meter hasn’t been shut off or run out of prepay credit, and check for a frozen condensate pipe in very cold weather (if visible and frozen, thaw with warm water — not boiling).

Specific diagnostic and next-step actions:

1. If a reset clears the code and the boiler runs normally, monitor for recurrence. If the fault returns intermittently, log when it happens and any conditions (power cuts, storms, very cold weather) to give the engineer a clear history.

2. If E135 persists after reset and the simple external checks, do not attempt internal repairs. E135 commonly indicates PCB/internal electronics, communication fault or an internal safety circuit failure and requires specialist diagnostic equipment and replacement parts.

3. Prepare information for the engineer: model and serial number, the exact error code and any secondary codes, what you tried to fix it (resets, condensate thaw, gas checks), and photos of the display.

4. If the boiler is unsafe (strange smells, burning smells, smoke or unusual noises) isolate the electrical supply and contact a Gas Safe engineer immediately.

When to call a professional:

- Call a Gas Safe registered heating engineer or Baxi support if the E135 stays on after a reset and basic checks, or if you are unsure about any step. Replacement or repair of PCBs, internal modules, or safety devices must be performed by a qualified engineer. Provide them with the code, photos and the history so they can diagnose faster.

Final notes:

- Do not attempt PCB or gas-component repairs yourself; this is a safety and warranty issue.

- Keep the boiler turned off if it is clearly unsafe. Otherwise you can leave it off and wait for the engineer to attend. Having the exact error code, model and a short fault history will speed up the repair visit.