Central Heating Not Working? How to Diagnose the Problem

Start With the Basics

Before concluding there's a serious fault, work through this quick checklist:

• Is the boiler switched on and showing power?
• Is the thermostat set above the current room temperature?
• Is the heating timer set correctly?
• Is the boiler pressure between 1 and 1.5 bar?

All Radiators Cold — Likely Causes

If no radiators are heating at all, the issue is usually at the boiler or central components:

• Boiler lockout: Check the error code display and follow the troubleshooting steps for that code
• Frozen condensate pipe: In very cold weather, the condensate pipe can freeze, shutting the boiler down
• Pump failure: The circulating pump moves hot water through the system. A failed pump means no circulation — a professional repair
• Zone valve failure: Most systems have motorised zone valves for heating and hot water separately. A stuck valve can block flow to the heating circuit

Some Radiators Cold — Likely Causes

• Air in the system: Bleed the cold radiators
• Sludge build-up: Cold spots at the bottom of radiators suggest sludge — a power flush may be needed
• TRV (thermostatic radiator valve) stuck: The pin inside the TRV valve can seize. Try removing the TRV head and lifting the pin manually
• Lockshield valve closed: The lockshield valve (on the return side of the radiator) may have been closed accidentally. Open it gradually

Radiators Hot But House Still Cold

If radiators are hot to the touch but the house doesn't heat up, the heating output may simply be insufficient for the property size. This could indicate an undersized boiler, poor insulation, or a need for additional radiators. Call us for a heating assessment.