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Problem Guides

No Heating

Radiators not heating, boiler faults, thermostat issues

10 free DIY guides · 24 total

If your radiators are cold but the boiler seems to be running, you're not alone — no heating is one of the top plumbing complaints every winter in the UK. The fault is usually with the boiler controls, a faulty diverter valve, airlocked radiators, or a circulation pump that has seized. Pinpointing whether it's a single zone, one radiator, or the entire system makes a huge difference to how quickly and cheaply you can get it sorted. These guides help you isolate the problem quickly so you know whether you can sort it yourself or need a Gas Safe engineer.

Most popular
1

Boiler shows a fault code or has locked out — what to do

Understanding boiler fault codes and when to reset vs. call an engineer

2

Boiler has locked out — how to reset it correctly

Boiler showing a lockout fault — what to do before calling an engineer

3

Boiler will not ignite

Boiler attempts to fire but fails — shows ignition fault code

Step 1 — What type of system do you have?

The diagnosis is different depending on your system — this helps us point you to the right guide.

All guides
Boiler Ignition Failure — Not Lighting
Boiler tries to light, clicks repeatedly, then locks out — not igniting successfully· 30 min–2 hrs
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Boiler has locked out — how to reset it correctlyFree
Boiler showing a lockout fault — what to do before calling an engineer· 5–10 min
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Boiler keeps firing and cutting off repeatedly
Boiler short-cycling — turns on and off every few minutes· 1–2 hrs (engineer)
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Boiler keeps losing pressure and switching off
Boiler pressure drops then boiler cuts out — repeated fault that keeps coming back· 15 min
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Boiler keeps switching itself off
Boiler fires up then cuts out after a few minutes· 5–10 min
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Boiler pressure too high — over 3 bar
Pressure gauge reading is in the red zone· 15–30 min
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Boiler programmer or timer not workingFree
Heating won't come on at scheduled times· 20–45 min
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Boiler shows a fault code or has locked out — what to do
Understanding boiler fault codes and when to reset vs. call an engineer· 15–60 min
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Boiler will not ignite
Boiler attempts to fire but fails — shows ignition fault code· 1–2 hrs (engineer)
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Central Heating Comes On at the Wrong TimesFree
Heating turning on unexpectedly, not following the programme, or on in summer· 15–45 min
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Central heating pump seized or humming — how to free it
Heating pump makes a humming noise but no water circulates· 30 min–2 hrs
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How to add central heating inhibitor to your systemFree
Adding Fernox F1 or Sentinel X100 inhibitor to protect central heating pipework· 20–40 min
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No heating because boiler pressure is too lowFree
Boiler showing low pressure warning — repressurise to restore heating· 10 min
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No heating in one zone only — upstairs or downstairs
Zoned system where only one circuit is not heating· 30–60 min
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One zone not heating — upstairs or downstairs cold
One floor or part of the house has no heating· 20–40 min
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Power flush — what it is, when you need one, and what it costs
Understanding power flushing and whether your heating system needs it· Half day (engineer)
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Programmer or timer not turning heating onFree
Central heating timer or programmer not activating the boiler at set times· 20–60 min
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Radiators are cold but boiler is firingFree
Boiler seems to be running but rooms stay cold· 20–60 min
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Room thermostat not workingFree
Thermostat doesn't seem to be controlling the heating· 20 min–2 hrs
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Smart thermostat (Nest/Hive) not controlling heatingFree
Nest or Hive thermostat is not turning boiler on· 20–45 min
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Underfloor Heating Thermostat Not WorkingFree
UFH thermostat blank, unresponsive, or not controlling the zone temperature correctly· 15–45 min
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Underfloor heating not working
Wet underfloor heating system not producing heat· 20–60 min
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Zone valve not opening — no heating in one area
Motorised zone valve stuck or not operating — one zone of the house has no heating· 1–3 hrs
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Zone valve stuck or not opening
Heating or hot water zone not responding· 5 min
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