Main Boiler Repairs

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Main Boiler Repairs London

Gas Safe registered engineers • 24/7 call handling • London wide

Call Now: 0203 868 6251 | Request a Call Back

Tell us the fault code and model. We will advise the safest next step.

Quick Navigation

• Safety First
• Quick Checks Before You Call
• Fault Code Table
• Most Searched Problems
• Why Main Boilers Fail
• Models We Repair
• Repair or Replace

Safety First

Smell gas? Turn off the gas supply at the meter if it is safe to do so. Open windows. Leave the property. Call the National Gas Emergency Service on 0800 111 999. Do not use switches, and do not use naked flames.

CO alarm sounding? Open windows immediately. Leave the property. Call 999. Do not re-enter until cleared by emergency services.

Boiler leaking heavily? Turn off the boiler at the controls. If safe, turn off the water supply. Call an engineer.

Quick Checks Before You Call

Before calling an engineer, these safe checks may resolve simple issues with your Main boiler.

Check the gas supply
Is gas working at other appliances in your home? If not, check your meter and any prepayment credit.

Check the pressure gauge
Main boilers display pressure on a gauge or digital screen. It should read between 1 and 1.5 bar when cold. If below 1 bar, you may need to re pressurise using the filling loop underneath the boiler.

Check the thermostat
Is the room thermostat set above current room temperature? Are the batteries working?

Check the timer or programmer
Is the heating scheduled to be on? Check the clock is set correctly.

Try a single reset
Locate the reset button on your Main boiler. Press once and wait. If the fault returns, do not keep resetting. Call an engineer.

Check the condensate pipe
In cold weather, the external condensate pipe can freeze. Look for a white plastic pipe exiting through an outside wall. If frozen, pour warm water over it gently.

Main Fault Codes Explained

Main is part of the Baxi Group and shares fault codes with Baxi and Potterton boilers. Codes vary by model, so always follow the code shown on your boiler display. If your code is not listed, tell us exactly what appears.

Most Searched Main Problems

E133 ignition lockout

E133 is the most common Main fault code. It means the boiler tried to ignite but failed, triggering a lockout. Common causes include gas supply issues, a faulty ignition electrode, or a blocked condensate pipe in winter. Check gas is on elsewhere in the home. Try one reset. If E133 returns, stop and call an engineer for Main boiler repair. This code is shared across Main, Baxi, and Potterton boilers.

E119 low pressure

E119 appears when system pressure drops below the minimum threshold. On Main boilers, you can re pressurise using the filling loop located underneath the boiler. If you top up and pressure falls again within days, there may be a leak in the system or a failing expansion vessel. Do not keep topping up. Call an engineer to find the cause.

E109 fan fault

E109 relates to the fan system on Main boilers. The fan must reach a certain speed before the boiler will fire, and the flue must be clear for safe operation. Fan faults can indicate a failing fan motor or debris in the flue terminal. Do not attempt to clear the flue yourself. Call an engineer for safe diagnosis.

Why Main Boilers Develop Faults

Main is part of the Baxi Group and shares components with Baxi and Potterton boilers. Here is what we commonly see.

Ignition electrode and lead wear

E133 ignition faults are common on Main boilers over 5 years old. The ignition electrode creates the spark, and over time it can wear or become coated with carbon. The ignition lead can also crack or degrade. Replacing these components usually resolves repeated E133 lockouts.

Pressure relief valve and expansion vessel

E119 low pressure faults often point to a failing expansion vessel or a weeping pressure relief valve. The expansion vessel absorbs pressure changes as water heats and cools. If the diaphragm fails or the air charge is lost, pressure drops occur frequently.

Diverter valve on combi boilers

The diverter valve directs hot water between your taps and radiators. When it wears or sticks, you may get heating but no hot water, or the reverse. This is common on Main combis over 8 years old.

PCB and electrical faults

The printed circuit board controls all boiler functions. E168 faults can indicate power supply issues or PCB failure. On older Main models, PCB faults become more common after 8 to 10 years. Diagnostic testing is needed to confirm.

Main Models We Repair

We repair Main combi, system, and regular boilers, including modern condensing models and older installations.

Parts availability is often strongest on newer Main models. Main shares parts with Baxi and Potterton, so availability is generally good. For older boilers, we check availability before attending where possible.

Repair or Replace Your Main Boiler?

We help you decide based on age, reliability, and parts availability.

Repair makes sense when

• Boiler is under 8 to 10 years old
• This is the first major fault
• Parts are readily available
• Boiler has been regularly serviced

Replacement may be better when

• Boiler is 10 to 12 years old or more
• You have had multiple breakdowns recently
• Parts are obsolete or hard to source
• The boiler is undersized for the property
• Energy bills are higher than expected for the property size

Our engineers give honest assessments. We focus on safety and reliability, not pushing unnecessary replacements.

Main Boiler Servicing

Regular servicing reduces breakdown risk and keeps your Main boiler running efficiently. We recommend annual servicing for all Main boilers.

A service visit includes inspection of key components, combustion analysis where appropriate, pressure checks, and cleaning where needed. We provide written service records.

Landlords and Letting Agents

We provide boiler repairs and gas safety certification for landlords across London.

Gas Safety Certificates (CP12)
Annual gas safety checks are a legal requirement for rental properties. We issue CP12 certificates and can send documentation directly to managing agents.

Repair and compliance
We can invoice agents directly and provide records for compliance files.

Main Repairs Across London

London wide coverage for Main boiler repairs. Book an engineer or view our London areas page.

Other Boiler Brands We Repair

Worcester • Vaillant • Ideal • Baxi • Glow worm • Viessmann • Potterton • Vokera • Alpha • Ferroli

View all brands

Main Boiler Repair FAQs

How quickly can you attend for a Main breakdown?

We offer same day attendance where slots are available. For no heating or hot water, we prioritise urgent breakdowns. Call our 24/7 line and we will advise availability.

Do you carry Main parts?

Our engineers carry common boiler parts. Main shares components with Baxi and Potterton, so availability is generally good. For less common parts, we source and fit them as soon as available.

Is it safe to reset my Main boiler?

A single reset is generally safe. If the fault returns after resetting, stop and call an engineer. Do not reset more than twice in 24 hours.

How much does a Main boiler repair cost?

Costs vary depending on the fault and parts required. We diagnose first and quote before any repair work begins.

Speak to Our Team

For safe next steps, call now or request a call back.

Call 0203 868 6251 | Book an Engineer

Gas Safe registered • 24/7 call handling • Quote before work