Central Heating Not Working — Diagnose It
Step 1: Check the Boiler
Is the boiler running? Check the display — is it showing a fault code? Is the pressure reading 1–1.5 bar? A common cause is low pressure — repressurise and try again.
Step 2: Check the Thermostat
Is the thermostat set higher than the current room temperature? Is it switched to 'heating on' mode? Check the timer/programmer — has the schedule been changed?
Step 3: Check Individual Radiators
Are all radiators cold, or just some? If just some, those radiators may have air (bleed them) or stuck TRVs (turn the head manually). If all radiators are cold but the boiler is running, the pump may be faulty.
Step 4: Check the Zone Valves
On systems with multiple zones (e.g., upstairs/downstairs), a stuck or faulty zone valve can prevent heat reaching one zone. Zone valves usually have a manual lever for testing.
When to Call an Engineer
If you've checked all of the above and the system still isn't working, it's time for a Gas Safe engineer. Common issues at this stage include a faulty pump, PCB problem, or failed zone valve.