DIY How To

Central Heating Faults

When heating systems don't work, there are various common faults, problems and solutions that you can carry out yourself. If the fault or problem still exists or is not listed below, it may be necessary to call a heating engineer.

Central heating faults


Possible Fault

Possible Solution

Boiler not working    


Thermostat set too low

Check room stats and boiler stats are working correctly.


Timer/programmer not working

Check it is switched on and set correctly.


Pilot light goes out

Re-light following the manufacturer's instructions. If fault persists have unit replaced.

Radiators not heating up

Circulating pump not working

Switch on pump and feel if there is a slight vibration. If it is not running check supply to pump, if it is still not working, shut system down and try to turn pump manually. Look for a large screw in middle, removing this usually reveals the slotted end of the pump spindle, turn until pump feels free.

Some radiators not heating up Timer or thermostat controlling zones not working Check timer or thermostat settings
  Airlock in pipes

Turn off the system and wait for pump to stop, if the pump has a bleed valve, unscrew it a couple of turns and listen for the release of air, close bleed valve when water appears.

If fault persists and the pump has a speed control try increasing and decreasing at half minute intervals.

Single radiator not heating up

Handwheel valve closed

Open the valve


Thermostatic radiator valve set too low or faulty

Adjust valve setting if this does not work unscrew head of valve on the knurled nut and us a pair of pliers to check the spindle will pull up and push down.


Lockshield valve incorrectly set

Remove lockshield cover and adjust valve setting until radiator seems as warm as others.


Inlet/outlet blocked by corrosion

Remove radiator flush out and replace.

Radiator cool at the top, warm at the bottom

Airlock at top of radiator

Bleed radiator to remove trapped air.

Radiator cool in middle, warm at the top and ends

Corrosion in radiator

Remove radiator flush out and replace

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