Just off the engine cover most car found relay mounting box, you can find a trace of the relay. Car lights, wiper, starter, air conditioners, electric seats, electric windows, anti-lock devices, suspension control, audio, etc. should spend control relay, it is one of the most used automobile electronic components, the current global market annual demand of over 1 billion.
The control relay has two main parts, one is the control system, and the other is the control system. Control relay has been able to control action, because when it's some kind of signal input control system, such as electricity, magnetism, heat, light and other physical reaches a certain value, can be controlled system (also known as the output circuit) is control the amount of mutation from zero to a certain value, or by mutations in a certain value to zero, so as to achieve control, protection, transfer and conversion of information and so on. A small current to control a large current, is to control the characteristics of the relay.

Automotive Control Relays technically demanding, because it has to adapt to vibration, heat, cold, moisture, and oil, salt, water and other aggressive harsh environments requiring long life, high reliability, small size, low consumption, and has electromagnetic compatibility, resistance flammable, fast response performance. Described as horse race again, but also horse can not eat. As automobile control relay, it must meet these requirements.
In conventional automotive lighting control relay, for example, there are three-legged, four-legged and five feet and other types of control relays. Control the headlights, front small lights and dashboard lights, cornering lights, rear lights, brake lights, reverse lights, fog lights, car lighting to play like. When the combination switch to ON file headlight, headlight relay control system (magnetic field coil section) will be energized to produce a magnetic field, alloy contacts immediately closed, controlled system of current conduction, thereby controlling the headlights turned on. When the combination switch to disconnect the power headlight OFF position, the magnetic field of the control alloy contacts disappear immediately separated, by the control system of the current cut-off, the headlights turned off.
The current car is still a mechanical control relay based, but Pat to develop solid-state relays. The key relay is reliability, because if the relay fails, the immediate cause paralysis of the system components, features, and even cause the entire car could not move. For example the starter relay fails, the car can not be powered on, although most ten dollars a starter relay, but without it the car will run the inconvenience.
Current domestic automobile control relay in accordance with the classification of vehicles have two major categories, one is the imitation of psyllium relay, mainly Germany and France to introduce technology vehicles matching, and the other is a fake Japanese car relay, mainly for the Japanese models supporting. In the international market, the well-known automobile control relay manufacturer Germany Bosch (BOSCH).