Oil boiler not working — no heat or hot water
Check the steps below first — if you're not confident, get it fixed safely today.
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Most likely cause & what to check
Check you have oil — look at the sight gauge or dip your tank with a dipstick. Running out of oil is the most common cause of oil boiler failure, especially in cold snaps when consumption is high.
Check the boiler display or indicator light. Most oil boilers go into "lockout" when they fail to fire after a set number of attempts. There will usually be a red light or fault indicator.
Press and hold the reset button on the boiler for 3 seconds, then release. The boiler will attempt to fire. If it fires successfully, monitor it for 30 minutes. If it locks out again, do not keep resetting — you may prime the combustion chamber with excess oil.
Check the oil filter is not blocked — this is a small canister on the oil supply pipe, usually near the boiler or the tank. A blocked filter prevents oil reaching the burner. If it looks dark or clogged, call an engineer to replace it.
Make sure the oil supply valve between the tank and boiler is fully open. It should be parallel with the pipe, not perpendicular.
In freezing temperatures, the oil line can freeze at the tank outlet or in exposed sections of copper pipe. If you suspect this, call an OFTEC-registered engineer — applying heat incorrectly to oil pipework is dangerous.
If the boiler fired but then cut out on the overheat thermostat (different from the lockout button), wait 20 minutes for it to cool, then press the small red button on the thermostat housing. If it keeps happening, the flue may be blocked or the heat exchanger scaled up.
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