What to do if the pilot light won't relight?

If the pilot light on your gas furnace or appliance refuses to stay lit or light at all, you should stop attempting to ignite it immediately to prevent a dangerous accumulation of unburned gas. First, turn off the gas control valve and wait at least five minutes for any residual gas to dissipate completely. Second, inspect the pilot assembly for blockages, dust, or corrosion, and check if the thermocouple tip is dirty or misaligned, as a faulty thermocouple fails to sense heat and automatically shuts the safety valve. Third, ensure the gas supply valve is fully open. If cleaning the thermocouple tip and following the manufacturer's lighting instructions precisely still fails to keep the pilot lit, you should turn off the gas supply and contact a licensed HVAC professional to replace the defective thermocouple or gas valve safely. You can verify success when the flame stays lit consistently.