How do you know if your radiator is not working properly?

You can tell if your radiator is not working properly by checking for cold spots on the radiator surface, which indicate inadequate heating. Additionally, if you hear gurgling noises or notice a leak around the radiator, these could signal trapped air or a malfunctioning valve. Lastly, if your room fails to reach the desired temperature despite the heating system being on, it may be a sign of radiator issues.