An E133 fault on a Baxi boiler means the burner has failed to establish or hold a flame, so the appliance has locked out.

It is the most common Baxi fault code, and the first checks are simple.

What E133 actually means

The boiler attempts ignition and looks for a flame signal. Without one, or if it loses one, it closes the gas valve and stops.

What you can safely check yourself

Check whether other gas appliances work. If the hob will not light, the supply is the problem.

Check prepayment meter credit if you have one.

Then reset. Two or three attempts maximum.

When to stop, and why

What causes it beyond the simple checks

A failed ignition or flame sensing electrode, a gas valve fault, low incoming gas pressure, a blocked or restricted flue, or a frozen condensate pipe in cold weather.

How Vantage can help

We are Gas Safe registered and cover Hertfordshire, Bedfordshire and Cambridgeshire, with an emergency line answered 24 hours a day.

Frequently asked questions

How many times can I reset a Baxi E133?

Two or three at most.

Could it be a frozen condensate pipe?

In winter, yes, and it often comes with a gurgling noise.

Is E133 expensive to fix?

It depends on the cause. Electrodes are relatively cheap, a gas valve is not.

What an engineer will do

An ignition fault is diagnosed by working along the sequence the boiler follows, rather than by replacing parts in hope.

Gas first. Working gas pressure is measured at the appliance with the boiler running, not just standing pressure with it off. An undersized or partly obstructed supply pipe gives adequate standing pressure and drops away under load, which produces intermittent ignition failure that gets wrongly blamed on the boiler.

Then the spark and the sense. The ignition electrode and the flame sensing electrode are inspected for wear, cracked ceramic, carbon deposits and correct gap. Worn or dirty electrodes are the single most common cause of ignition lockouts on an otherwise healthy appliance, and they are inexpensive.

Then the flue and condensate. A restricted flue or a condensate trap that has silted up or frozen prevents proper combustion. In winter the condensate is checked early, because it is the most common seasonal cause.

The gas valve last. It is the expensive component and the least likely of the four, so it is tested rather than assumed.

Stopping it coming back

• Have it serviced annually. Electrode wear is exactly what a service catches before it becomes a December breakdown. See boiler servicing.
• Insulate the condensate pipe where it runs outside. A frozen condensate is preventable and it is the most common winter lockout we attend.
• Keep the flue terminal clear of vegetation, nests and stored items.
• If you are on a prepayment meter, keep some credit in hand through cold weather, because a boiler working hard uses more than you expect.

Related fault codes

Other Baxi codes: Baxi E110 · Baxi E125

The same problem on other makes (ignition and flame faults): Vaillant F28 · Vaillant F29 · Vaillant F27 · Ideal L2 · Ideal F2 · Glow-worm F28 · Viessmann F4

See also our guide to boiler not firing up, the full boiler advice section, and boiler repair.

When to call an engineer

If the fault keeps returning after a reset, it is telling you something is degrading rather than broken. Call 01462 506374 and we will diagnose it properly rather than swapping parts and hoping. Gas Safe registered 956889, 2 years on our own labour.