Common Baxi Boiler Problems and What Usually Causes Them

The most common Baxi boiler problems are low water pressure (E118 or E119), failure to light (E133 or E128), overheating and circulation faults (E110 and E125), control board lockouts after a power cut (E168), and a combi that gives heating but no hot water. Most of these show a fault code on the display, and a few can be cleared safely at home: topping up the pressure, thawing a frozen condensate pipe, or resetting once after a power cut. Anything beyond that sits inside the casing and needs a Gas Safe registered engineer. Below is how to tell the problems apart, what you can check yourself and when to stop.

What Are the Most Common Baxi Boiler Problems?

On current Baxi boilers, most faults fall into five groups: pressure, ignition, circulation, electrics and hot water. The fault code on the display tells you which group you are in.

Current Baxi combis, including the 200, 400, 600 and 800 ranges and the earlier Duo-tec and Platinum models, use three-digit codes that start with E1. Potterton and Main boilers come from the same group and share the same code list, so a Potterton E133 means the same as a Baxi E133. The display often shows the code in two halves, E1 and then 33, which is why people search for "E1 33". Our guide to reading Baxi E1 fault codes goes through each code in turn. Older Baxi boilers use shorter codes such as E10, E28 or E53, and a few have no display at all, so check the manual for your exact model. The model name is on the front panel or the data badge under the boiler.

Write the full code down before you press anything. It may vanish after a reset, and it is the single most useful thing to tell an engineer.

Why Does My Baxi Boiler Keep Losing Pressure?

A Baxi that keeps showing E118 or E119 is losing water from the heating system. Topping up gets it running again, but the real fault is wherever the water is going.

Look at the pressure gauge on the front of the boiler. With the heating off it should normally sit at around 1 to 1.5 bar. If it is well below that, top it up through the filling loop as the manual describes, then reset. If the code comes back within days or weeks, the usual causes are a small leak on a radiator valve or a joint under the floor, a pressure relief valve that drips water out of a copper pipe on the outside wall, or an expansion vessel that has lost its air charge. A gauge that climbs towards 3 bar when the heating is on and falls when it cools often points to the expansion vessel.

Do not keep topping up week after week. Fresh water brings in oxygen, which speeds up corrosion inside radiators and the boiler, and the leak can be quietly soaking into a ceiling below.

Why Won't My Baxi Boiler Fire Up?

If the boiler clicks, tries to light and then shows E133 or E128, it is an ignition lockout. The common causes are no gas reaching the boiler, a frozen or blocked condensate pipe, or a worn ignition or flame-sensing electrode.

You can safely check three things. Make sure your hob or other gas appliances work and a prepayment meter has credit. Check that the gas valve under the boiler has not been knocked off. In cold weather, look at the plastic condensate pipe where it leaves the house: if it is frozen, pour warm, not boiling, water along it and reset once. If those are fine and the code returns, the electrode, the gas valve, the fan or the control board needs testing by an engineer. Our page on why a Baxi boiler won't fire up covers these ignition checks in more depth.

Why Is There Heating but No Hot Water From My Baxi Combi?

When a Baxi combi heats the radiators but the taps run cold, or gives hot water but leaves the radiators cold, the diverter valve is the usual suspect. It is the part that sends hot water either to the radiators or to your taps.

A diverter valve that sticks in one position gives you one service and not the other. Radiators that get warm while you run a hot tap is another sign. Before assuming that, check the simple things: the hot water setting is turned up, the boiler is not in a summer or heating-only mode, and cold water pressure at the kitchen tap is normal, because a combi needs enough mains flow to start. If all that is fine, our explainer on what a diverter valve does and how it fails sets out the symptoms. Replacing the valve or its actuator is engineer work, and on many combis it is a routine repair rather than a reason to change the boiler.

What Causes Overheating, Kettling and E125 on a Baxi?

E110 (overheat) and E125 (circulation fault) usually share one cause: water is not moving through the boiler fast enough to carry the heat away. Kettling, a rumbling or boiling sound from the boiler, is often the same problem heard rather than displayed.

The usual reasons are a pump that is sticking or wearing out, sludge narrowing the heat exchanger, air trapped after work on the radiators, low pressure, or every radiator valve closed at once. Check the pressure, make sure several radiators are open, bleed any that are cold at the top, then reset once. If the code or the noise comes back, do not keep resetting it, because each restart heats the same trapped water again. An engineer will test the pump and the flow through the boiler, and if sludge is the cause they should tell you so plainly rather than only replacing the part that failed first.

What Does E168 or a Blank Display Mean on a Baxi?

E168 is a general control board lockout, and it very often appears after a power cut, a tripped fuse or electrical work nearby. A blank display usually means no power is reaching the boiler at all.

For a blank screen, check the fused spur switch next to the boiler, the fuse in it and your consumer unit. For E168, switch the boiler off at the spur for a minute and back on. If the code returns, or appears with no obvious electrical event, the board, its wiring or a component it controls needs testing. Baxi also has E97, which points to a problem with the mains electricity supply rather than the boiler itself. Water getting inside the casing can damage the board, so an engineer should look for any leak before replacing it.

When Should You Call an Engineer, and Is a Baxi Worth Repairing?

Reset once after the safe checks above. If the same code returns, stop and book a repair. Most Baxi faults come down to a single part and are worth fixing.

Call straight away, and do not reset, if you smell gas, see soot or scorch marks around the boiler, or hear loud, continuous banging. If you smell gas, turn the supply off at the meter if you can, open windows, avoid electrical switches and ring the National Gas Emergency Service on 0800 111 999. Work inside the boiler casing must by law be done by a Gas Safe registered engineer. Repair is the wrong answer on an old Baxi with a leaking heat exchanger, a board and a pump failing at the same time, or parts that are no longer made, and a good engineer will say so rather than keep patching it. When you contact us for a Baxi boiler repair in London, have the model name, the full fault code and whether you have already topped up or reset it. That is usually enough for us to know which parts to bring.