Oil Boiler Repair for Breakdowns and Lockouts
Most oil boiler repairs come down to the fuel not reaching the burner cleanly or the burner not lighting it properly. Lockouts, a boiler that fires then cuts out, smoke at the flue or soot around the casing usually point to a blocked filter or nozzle, a fuel supply problem, or a worn burner component. Check the simple things first, then call us and we will diagnose the fault properly rather than guess at parts.
Check these before you call
A few quick checks can save a visit, and they help us if you do need one:
- Tank level: read the sight gauge or gauge on the tank. A low tank can draw sludge and water into the line.
- Recent delivery: a boiler that stops just after a delivery may have stirred-up sediment in the filter.
- Power and controls: check the boiler has power and the thermostat and timer are calling for heat.
- Reset once: press the lockout reset a single time. If it locks out again, leave it and call us.
Why a reset should only be tried once
Each failed ignition attempt can push unburnt oil into the combustion chamber. Pressing reset repeatedly lets that oil build up, and when the boiler does finally light it can burn dirty, smoke heavily or cause a puff-back. If one reset does not bring the boiler back, the fault needs finding, not forcing. Our guide on a boiler that keeps locking out explains the common causes.
Common oil boiler faults we repair
Blocked fuel filters and nozzles are among the most common causes of breakdowns. Sludge and water in the tank, a kinked or damaged oil line, an air lock after running out of oil, or a sticking fire valve can all starve the burner. On the burner itself, worn electrodes, a failing photocell, a tired fuel pump or a faulty control box can stop it lighting or holding a flame.
A boiler that smokes, smells or leaves soot around the casing is burning poorly. That usually means the combustion needs setting up again, the nozzle needs changing or the heat exchanger and flue need cleaning. Turn it off if you see heavy smoke, and call us.
When repair stops making sense
Most faults are worth fixing. Repair becomes poor value when the same boiler fails repeatedly, when the heat exchanger is corroded or leaking, or when parts for an older model are hard to get. In that case we explain the options, including a new condensing oil boiler or a switch to a heat pump, and leave the decision with you.
Regular servicing prevents many of these breakdowns, because the nozzle, filter and combustion are checked before winter. Our oil boiler servicing page covers what a service includes. For urgent problems, see our emergency plumber page, and for gas boilers see our boiler repair page.
We cover Kelso, the Scottish Borders and East Lothian.
Oil Boiler Repair questions
Why does my oil boiler keep locking out?
Usually because the burner cannot light or hold a flame. Common causes are a blocked filter or nozzle, water or sludge in the fuel, an air lock after running low, or a worn burner part such as the photocell or electrodes.
Is it safe to reset an oil boiler?
Pressing reset once is fine. If it locks out again, stop and call an engineer, because repeated resets can flood the chamber with unburnt oil.
Can you repair any make of oil boiler?
We work on all makes. Telling us the make and model when you call helps us bring the most likely parts.
My boiler stopped after an oil delivery. Why?
A delivery can stir up sediment in the tank, which then blocks the filter or nozzle. It usually needs the filter cleaning or changing and the burner checking.
Get Your Free Quote
Tell us about your project — we'll respond within one working day.