An oil boiler that has stopped usually has a fuel problem, an ignition problem or a flame-detection problem. We diagnose which before quoting, because swapping parts until it lights is expensive and it does not tell you why it stopped. If a boiler is genuinely beyond economic repair, we will say so rather than sell you a repair.
Start here: the reset button
Nearly every oil burner has a red reset button with a light in it, either on the control box on the burner itself or on the boiler fascia. If the boiler is dead and that light is on, the burner has locked out. Lockout is not a fault in itself – it is the safety system doing exactly what it is supposed to do, which is to stop pumping fuel into an appliance that did not prove a flame.
Every reset attempt sprays another dose of kerosene into a combustion chamber that has already failed to ignite it. Do that repeatedly and you get unburnt oil pooling in the chamber, which at best makes an appalling mess and at worst ignites all at once when the boiler finally does light. If two resets have not fixed it, something is genuinely wrong and pressing the button again will only make the repair bigger.
There is a longer explanation of lockouts, what triggers them and what the control box is actually doing in our guide to oil boiler lockouts.
The things worth checking yourself first
None of these need an engineer, and between them they account for a surprising share of the calls we get in cold weather.
- Is there oil in the tank? Sight gauges stick, float gauges lie and electronic gauges go flat. Check physically with a dipstick if the tank allows it. Running dry is the single most common cause of a boiler that will not light, and it has an important consequence covered below.
- Is the fire valve still open? The fire valve is a thermal cut-off in the oil line, usually with a sensor near the boiler. If it has tripped – sometimes from nothing more than a hot summer or a knock – the fuel supply is shut and the boiler will lock out on every attempt.
- Is the tank valve open? Obvious, and worth ruling out, particularly after any work on the tank.
- Has the electrical supply been interrupted? Check the fused spur, the RCD and any boiler isolator switch. Many oil boilers sit on their own spur that is easy to knock.
- Is the thermostat or programmer actually calling for heat? Flat batteries in a wireless room thermostat present exactly like a dead boiler.
- Is the condensate pipe frozen? On a condensing oil boiler in cold weather, a frozen external condensate pipe will shut the boiler down. This is seasonal, predictable and preventable – see frozen condensate pipes.
Running out of oil, and why it matters
If a tank runs dry the burner does not simply stop. The pump draws air into the fuel line, and air in the line is why the boiler will not restart on its own once you have had a delivery. The line needs bleeding at the pump, and on many burners the pump needs priming properly rather than just being run until it catches.
There is a second, less obvious problem. The bottom of an oil tank is where sludge, water and sediment settle over the years. Running the level right down draws that layer straight into the fuel line, which blocks filters, can reach the nozzle, and occasionally contaminates the pump. It is why a boiler that ran dry in December can turn into a filter change in January and a pump in February. Keeping a working reserve in the tank is not fussiness – it is maintenance.
The full restart procedure, including the order to bleed in, is in restarting an oil boiler after running out.
The faults we actually find
Once the easy causes are eliminated, oil boiler repairs cluster into a fairly short list.
| Symptom | Common cause | What is involved |
|---|---|---|
| Locks out immediately, no attempt to fire | Fire valve tripped, no fuel, or a control box fault | Fuel and electrical checks first; control box is a last conclusion, not a first guess |
| Fires, runs a few seconds, locks out | Photocell dirty or failing – the flame lights but is not proved | Clean or replace photocell, then verify with a combustion run |
| Fires but runs rough, smoky or noisy | Worn nozzle, wrong pump pressure, incorrect electrode gap, or air in the line | Burner strip and full recommission with an analyser |
| Intermittent – works, then does not | Failing pump coupling, marginal photocell, or a partially blocked filter | Needs running under load and measuring, not eyeballing |
| Smell of oil around the boiler | Leaking flexible hose, pump seal or filter bowl seal | Trace and repair – never ignore, and never assume it is ‘always smelled like that’ |
| Soot marks or smoke from the flue | Badly tuned burner or a blocked heat exchanger | Treat as urgent. Incomplete combustion means carbon monoxide. |
| Boiler short-cycles | Heating system problem more often than boiler problem – sludge, poor flow, or an oversized appliance | Diagnose the system, not just the appliance |
Turn the boiler off and ventilate. Incomplete combustion produces carbon monoxide and an oil appliance can produce it just as readily as a gas one. Every property with an oil boiler should have a working, in-date CO alarm sited to the manufacturer’s instructions – they are inexpensive, and an oil boiler is precisely the kind of appliance they exist for.
Repair or replace
There is a point at which repairing an old oil boiler stops making sense, and we would rather have that conversation honestly than keep returning to the same appliance. The things that push us towards recommending replacement are these:
- The combustion chamber lining has broken down, on a model where it is not a serviceable part.
- The heat exchanger is corroded through, or baffles have warped enough that flueways cannot be sealed properly.
- Parts availability has gone – some older appliances are genuinely unsupportable now.
- The efficiency figures have fallen far enough that the fuel saving from a modern condensing appliance would pay for a large part of the difference.
- It has needed three call-outs in two winters. At that point you are renting reliability rather than owning it.
Equally, plenty of twenty-year-old oil boilers are mechanically sound and worth keeping. A well-built cast iron appliance that has been serviced properly does not owe anybody an apology. We will tell you which one yours is.
Not sure whether yours is worth repairing? Describe the symptoms on the phone – we can usually narrow it down before anyone gets in a van.
Questions we get asked about this
How quickly can you get to a breakdown?
It depends on the day and where you are, but no heat and no hot water in cold weather is treated as urgent. Call rather than email – the phone is the fast route, and we can often tell you on the call whether it is something you can resolve yourself in five minutes.
Do you charge a call-out fee?
You will be told what the visit costs before we set off, and you will not get a surprise. What we will not do is give you a repair price over the phone before anybody has looked at the appliance – that is how people end up with a quote that changes on the doorstep.
Can you repair any make of oil boiler?
We work on all the common makes – Grant, Firebird, Warmflow, Worcester Danesmoor, Mistral, Boulter, Trianco and the rest. Parts availability is the real constraint on very old appliances, and we will tell you straight away if we think a part is going to be a problem.
The boiler works, but the radiators are barely warm. Is that a boiler fault?
Usually not. Poor radiator performance with a boiler that is running is far more often a circulation problem – sludge, a failing pump, air, or a system that has never been balanced. It is a different diagnosis and a different fix. See radiators cold at the bottom.
Should I just keep pressing reset until it goes?
No. Two attempts maximum. Each one puts more unburnt fuel into the chamber, and the damage from repeated resets is entirely self-inflicted.
My boiler is outside. Does that change anything?
External oil boilers suffer more from weather – water ingress into the burner housing, corroded casings and frozen condensate are all more common. They also tend to get ignored because nobody walks past them. If yours is outdoors, the annual service matters more, not less.
What happens when you call
Call and describe it
You speak to an engineer, not a call centre. Most jobs can be narrowed down on the phone.
We look at it properly
A real diagnosis before a price, and a straight answer if it is not worth doing.
A written quote
Itemised, so you can see what you are paying for.
The job, and the paperwork
Certificates where the work needs them, and what will need attention next.
Where we do this work
Across Norwich and the whole of Norfolk. If you are on the edge of the county, call and ask — we will tell you honestly whether we are the right people.
- Norwich
- Wymondham
- Dereham
- Attleborough
- Aylsham
- North Walsham
- Cromer
- Diss
- Loddon
- Long Stratton
- Watton
- King's Lynn
Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.