Most cars are now fitted with electric windows rather than those that are operated manually. The way in which the electric windows above the doors of a vehicle are opened and closed when the electric window switch is pressed is through a door window relay.

A door window relay works through an electromagnet that is present in the relay component. Electricity from the vehicle’s battery is introduced to this magnet with the result that a magnetic field is created. This magnetic field, which will exist for as long as the electromagnetic is charged, has the effect of pushing a switch into position which causes the window to move up and down.

In certain cases, the door window relay will only operate when the vehicle’s ignition is switched on, although there are some models of door window relay, commonly known as power window relays, where the connection between the battery and the relay is maintained for a short period of time even when the ignition keys have been removed.

If an individual door window fails to open it may indicate that the door window relay is no longer operating and will need to be replaced immediately, especially if the window is stuck in the “open” position.