Sime Boiler Repairs

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Sime 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 Sime 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 Sime 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
Sime boilers display pressure on the front panel. 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.

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 Sime 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.

Sime Fault Codes Explained

Sime boilers display numeric fault codes, but formats vary by model and control panel. Always follow the code shown on your boiler display. If your code is not listed, tell us exactly what appears.

Most Searched Sime Problems

01 ignition lockout

Code 01 is one of the most common Sime fault codes. 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 the code returns, stop and call an engineer for Sime boiler repair.

04 low pressure

Code 04 appears when system pressure drops below the minimum threshold. On Sime boilers, you can re pressurise using the filling loop. 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.

02 flame lost during operation

Code 02 indicates the boiler ignited successfully but the flame was lost during operation. This can point to an intermittent gas supply issue, a faulty flame sensor, or a problem with the gas valve. Do not keep resetting. Call an engineer for Sime boiler diagnosis.

Why Sime Boilers Develop Faults

Sime boilers are installed across UK homes. Here is what we commonly see.

Ignition electrode wear

Code 01 ignition faults are common on Sime boilers over 5 years old. The ignition electrode creates the spark, and over time it can wear or become coated with carbon.

Pressure relief valve and expansion vessel

Code 04 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 Sime combis over 8 years old.

PCB and electrical faults

The printed circuit board controls all boiler functions. On older Sime models, PCB faults become more common after 8 to 10 years. Symptoms include erratic displays or random lockouts.

Sime Models We Repair

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

Parts availability is often strongest on newer Sime models. For older boilers, we check availability before attending where possible.

Repair or Replace Your Sime 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.

Sime Boiler Servicing

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

Sime Repairs Across London

London wide coverage for Sime 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

Sime Boiler Repair FAQs

How quickly can you attend for a Sime 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 Sime parts?

Our engineers carry common boiler parts. For Sime specific components, we source and fit them as soon as available.

Is it safe to reset my Sime 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 Sime 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