A cars radiator is a central part of the engines cooling system. Responsible for removal of heat from the engine coolant, the radiator system cools the liquid by allowing fresh external air to pass over a network of thin pipes, losing heat to the atmosphere.
A key component of the cooling system is an electric fan, which sits between the radiator and bonnet grille and blows fresh air across the radiators cores to assist with cooling.
As the electric fan is not always needed, it is controlled by a temperature switch and motor relay. This ensures that the fan is activated when the coolant exceeds a specified temperature.
A <Model> radiator fan motor relay can break over time and is probably one of the most common causes of electric radiator fan failure. In most cases when a <Model> motor relay fails the fan will not start when needed. In some cases the fan will run at all times.
Other things to check for include fuses, wiring, fan motor or the temperature switch.