Keston Boiler Repairs
Experienced Keston Boiler Repairs specialists
Available 24 hours a day, 7 days a week
Insurance approved
All parts guaranteed for a year
Fully Gas Safe trained engineers
Keston Boiler Repairs London
Gas Safe registered engineers • 24/7 call handling • London wide
Call Now: 0203 868 6251
Tell us the fault code and model. We will advise the safest next step.
Common Keston models we repair include C36, C40, C55, Heat, and Celsius series, with frequent calls for codes E01, E02, E03, and E04.
We fix Keston boiler fault codes, no heating, no hot water, lockout, leaking, and low pressure across London.
We also offer boiler servicing and boiler installation across London.
Quick Navigation
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 Keston 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
Pressure should read around 1.0 to 1.5 bar when cold. If below 1 bar, you may need to repressurise 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 Keston 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.
Keston Fault Codes
Note: Keston fault codes vary by model and generation. If your code is not listed here, call us with the exact code and model and we will advise the safest next step.
Common Keston fault codes and what to do
| Code |
What It Means |
What To Do |
| E01 |
Ignition failure (failed to light) |
Check gas supply and whether other gas appliances work. In freezing weather, check condensate pipe. If still locked out, call an engineer. |
| L2 |
Ignition lockout (multiple failed attempts, model dependent) |
Check gas supply and condensate pipe. Reset once. If it returns, call an engineer. |
| E02 |
Flame detection or safety lockout (model dependent) |
Do not keep resetting. Call an engineer for safe checks and testing. |
| E03 |
Overheat or airflow issue (model dependent) |
Check pressure is in range and radiators are open. If it returns, call an engineer. |
| E04 |
Low system pressure (model dependent) |
Top up to 1.0 to 1.5 bar. If it drops again within days, call an engineer. |
| Fan fault |
Fan fault or flue issue |
Call an engineer. Do not remove covers. |
Most Searched Keston Problems
If you are seeing a lockout, loss of hot water, or your Keston boiler keeps resetting, tell us the fault code and model and we will confirm the safest next step.
E01 – ignition failure
E01 is the most common Keston fault code. The boiler tries to ignite but fails to light. 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 lockout returns, stop and call an engineer.
E04 – low pressure
If your Keston shows E04, system pressure has dropped below the minimum threshold. Top up via the filling loop to around 1.0 to 1.5 bar when cold. If pressure drops again within days, there may be a leak in the system or a failing expansion vessel. Call an engineer to find the cause.
L2 – multiple ignition failures
L2 indicates the boiler has failed to ignite after multiple attempts and has locked out. This is similar to E01 but indicates repeated failures. Check gas supply and condensate pipe. Reset once. If it returns, call an engineer for diagnosis.
No hot water but heating works
On Keston combi boilers, you may get heating but no hot water, or the reverse. This often points to a diverter valve issue. The diverter valve directs hot water between taps and radiators. When it wears or sticks, hot water delivery becomes unreliable. Call an engineer for diagnosis.
Why Keston Boilers Develop Faults
Keston boilers are manufactured in the UK by Ideal Heating and known for build quality. Here is what we commonly see.
Ignition electrode wear
Ignition faults (E01, L2) can occur when the ignition electrode wears or becomes coated with carbon. Condensate blockages in winter can also contribute to repeated lockouts.
Low pressure and expansion vessel faults (E04)
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 can occur.
Overheat and airflow issues (E03)
E03 can indicate overheating or restricted airflow. This may be caused by a circulation problem, blocked pump, or closed radiator valves. The boiler locks out to protect itself.
Fan and flue faults
Fan faults prevent safe combustion and flue gas extraction. The boiler will lock out for safety. Causes include fan motor failure, wiring faults, or flue blockages.
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.
Keston Models We Repair
We repair Keston combi, system, and regular boilers in London, including:
C range: C36, C40, C55, C40P, C55P
S range: S30, S40, S55
Heat range: Heat 45, Heat 55
Celsius range: Celsius 25, Celsius 30
Older models: Earlier Keston units
Keston is manufactured in Hull by Ideal Heating. Parts are generally available. We check availability before attending and advise honestly if repair is not viable or cost effective.
Repair or Replace Your Keston Boiler?
We help you decide based on age, reliability, and parts availability.
Repair makes sense when
- Boiler is under 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 12 to 15 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.
Keston Boiler Servicing
Annual servicing reduces breakdown risk and keeps your Keston boiler running efficiently. See Boiler servicing London.
Landlords and Letting Agents
We provide boiler repairs and gas safety certification for landlords across London. See Landlord gas safety certificate (CP12).
Keston Repairs Across London
London wide coverage for Keston boiler repairs. Book an engineer or view our London areas we cover.
Have your postcode and fault code ready and we will confirm the quickest appointment slot.
Other Boiler Brands We Repair
Worcester • Vaillant • Ideal • Baxi • Glow-worm • Viessmann • Potterton • Vokera • Alpha • Ferroli
View all brands
Keston Boiler Repair FAQs
How quickly can you attend for a Keston 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 Keston parts?
We stock common Keston parts and can source through the Ideal Heating network. For less common parts, we can usually source within 24 to 48 hours.
Is it safe to reset my Keston boiler?
Try one reset. If the fault returns after resetting, stop and call an engineer. Do not keep resetting.
How much does a Keston boiler repair cost?
Costs vary depending on the fault and parts required. We diagnose first and quote before any repair work begins.
Related Services
Speak to Our Team
For safe next steps, call now.
Call 0203 868 6251 | Book an Engineer
Gas Safe registered • 24/7 call handling • Quote before work
