Safety time to establish flame exceeded
The 133 error code on Baxi boilers indicates safety time to establish flame exceeded.
Baxi 133 means: safety time to establish flame exceeded. On this component the documented failure modes are no gas reaching the burner, or the gas supply is shut off, flue or air intake blocked or restricted or ignition or detection electrode dirty, worn or out of position. A Gas Safe registered engineer should diagnose the root cause.
What Does 133 Mean
The 133 code is shown by the boiler’s control board when it detects safety time to establish flame exceeded. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows 133 and the boiler stops until the fault is cleared |
Common Causes
The manufacturer does not publish a cause list for this specific code. The causes below are the failure modes documented for the same component on other boilers, confirmed by the service literature of 6 different manufacturers.
| Cause |
|---|
| No gas reaching the burner, or the gas supply is shut off |
| Flue or air intake blocked or restricted |
| Ignition or detection electrode dirty, worn or out of position |
| Faulty gas valve, or its wiring and connector |
| Control board (PCB) faulty |
Safety Warning
133 is a gas-related fault. Never attempt to repair or adjust the gas valve, burner assembly, or flue system yourself. All gas work must be carried out by a Gas Safe registered engineer (UK) or licensed HVAC technician (US). Repeated resets after ignition failure can cause unburnt gas to accumulate inside the combustion chamber — this is a serious safety hazard. If you smell gas at any point, turn off the gas supply at the meter, open windows, leave the property, and call your gas emergency service immediately. Gas-related fault. Do not open the boiler casing or attempt repairs to the gas valve, burner, ignition or flue. Repeated resets are unsafe. Diagnosis and repair must be carried out by a Gas Safe registered engineer.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
1. Note the exact error code and check the manufacturer's installation and service manual for specific guidance. 2. Check all visible wiring connections for security and condition. 3. Power cycle the boiler — switch off at the mains for 30 seconds, then switch back on. 4. If the fault recurs, check the fault history for related or recurring codes. 5. Inspect the boiler for any obvious signs of damage, leaks, or unusual sounds
How to Fix It
Check that the gas service valve is open and that other gas appliances in the property work. If they do not, the problem is the gas supply, not the boiler.
Inspect the flue and air intake along their whole length, including the outside terminal, and clear any obstruction or debris.
Inspect the ignition and detection electrode: clean off any deposits, check the gap and position against the manual, and replace it if it is worn.
Check the gas valve connector and wiring for continuity, then test the valve coil resistance against the manual; replace the valve if it is out of range.
Only after every other check: verify the board’s supply and connections, and replace the board — fitting the correct boiler chip card or coding key where the model requires one.
Refer to the Baxi service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Baxi models that can display fault code 133:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Baxi models | — | Possible |
Frequently Asked Questions
Check that the gas service valve is open and that other gas appliances in the property work. If they do not, the problem is the gas supply, not the boiler. According to the technical documentation, this is the first check on the list for 133.
133 is classified as a high-severity fault: it involves gas, combustion or flue components. Do not keep resetting the boiler and do not attempt the repair yourself — call a Gas Safe registered engineer.