What the E133 code means
Potterton manuals for the Promax, Titanium, Gold and Assure ranges all describe E133 in the same words: "interruption of gas supply or flame failure". Potterton is part of the Baxi group and these boilers share a lot of their design with Baxi models, so the code works the same way as Baxi E133.
When the boiler needs heat, the fan starts, the gas valve opens and the electrode sparks. A flame sensor then checks the burner has lit. If no flame is detected after the permitted attempts, the gas is shut off and the boiler locks out with E133.
How E133 looks on your display
This depends on the range, and it catches a lot of people out:
- Promax, Titanium and Gold: the display can only show two characters at once, so E133 appears as "E1" alternating with "33".
- Assure: the display shows 133 with a symbol beside it. An R means you can try a reset. The Assure also has a related code, 135, for an interruption of the gas supply caused by an internal error.
Common causes of E133
No gas reaching the boiler
A prepayment meter out of credit, a gas isolation valve knocked closed or a supply problem in the street all stop the boiler lighting. Check other gas appliances first.
Frozen condensate pipe
In a hard frost the condensate pipe can freeze where it runs outside. Water backs up inside the boiler and it cannot light, so E133 is very common on cold mornings.
Ignition electrode
The electrode wears and can drift out of position. The boiler may click repeatedly without lighting.
Gas valve, fan, flue or control board
If gas is available and the pipe is clear, the fault is inside the boiler. The gas valve, fan, flue and control board all need testing by an engineer.
| Cause | Typical sign | Who fixes it |
|---|---|---|
| Prepayment meter out of credit | Hob will not light either | You, by topping up |
| Gas isolation valve closed | Handle across the pipe under the boiler | You, by opening it |
| Frozen condensate pipe | Freezing weather, gurgling from the boiler | You, by thawing it |
| Worn ignition electrode | Clicking without lighting, fault more frequent | Gas Safe engineer |
| Gas valve or control board | Gas supply fine, E133 every time | Gas Safe engineer |
Safe checks you can do yourself
- Try your hob or another gas appliance. If nothing lights, the problem is the supply, not the boiler.
- If you have a prepayment meter, check the credit and top up, then follow the meter's instructions to restore the supply.
- Check the gas isolation valve under the boiler is open, with the handle in line with the pipe.
- In freezing weather, find the condensate pipe outside and thaw it with warm (not boiling) water or a hot water bottle. Our frozen condensate pipe guide shows how.
- Check the fused spur is on and the thermostat and timer are calling for heat.
- Reset the boiler the right way for your model. On an Assure, press Reset for about one second, as holding it for more than two seconds will not reset it. On a Promax, Titanium or Gold, turn the selector to the reset position and hold for about five seconds. Try no more than two or three times.
If you smell gas, do not reset the boiler or use electrical switches. Turn off the gas at the meter if it is safe to do so, open doors and windows, leave the property and call the National Gas Emergency Service on 0800 111 999.
When to call a Gas Safe engineer
If gas is reaching your other appliances, the condensate pipe is clear and E133 keeps coming back, call a Gas Safe registered engineer. They will usually check the gas pressure at the boiler, the electrode and its gap, the gas valve, the fan and flue, and the condensate trap. On an Assure, an engineer can also read the stored fault history.
If your Potterton is still under warranty, contact Baxi customer support first, as it handles Potterton warranty repairs. Using another engineer could affect the cover.
Spotting a pattern
Before the engineer arrives, think about when E133 appears. A fault that only shows on frosty mornings points to the condensate pipe. One that appears after the prepayment meter has been topped up points to the supply. One that happens at random and is getting more frequent is more likely to be a worn electrode or a gas valve starting to fail. Passing on that pattern helps the engineer focus on the right part first, which usually means a shorter visit and a smaller bill.
Typical repair costs in the UK
Typical ranges only. Costs depend on the model, the part and your area.
| Job | Typical UK cost |
|---|---|
| Topping up credit or thawing the pipe | Free |
| Engineer call-out and diagnosis | Typically £80 to £150 |
| Ignition electrode replacement | Typically £100 to £180 |
| Gas valve replacement | Typically £250 to £450 |
| Insulating or rerouting the condensate pipe | Typically £100 to £250 |
How to stop E133 coming back
Keep prepayment credit topped up in winter, when gas use climbs quickly. If E133 mostly appears on frosty mornings, ask an engineer about insulating the condensate pipe or rerouting it indoors. The Assure manual notes this pipe must only be altered by a qualified professional. An annual service lets the engineer clean and check the electrode and condensate trap before they cause a lockout. See our boiler service cost guide for what is included. For other Potterton codes, see our Potterton fault codes page.