The 4 and 5 pins are all single-pack relays, that is, there is only one coil and can only control one channel.
The two pins of the 4-pin automotive relay are connected to the internal coil of the relay, and the other two pins are connected to the internal contacts of the relay. When the power is not applied, the two contacts are disconnected, which is called a normally open contact; A contact is closed and is called a normally closed contact. The normally open contact Panasonic is represented by a, and the normally closed contact Panasonic is represented by b. Normally open contacts are mainly used in automobiles.

The 5-pin automotive relay also has two pins connected to the internal coil of the relay, and the other three pins are connected to the internal contacts of the relay. The relay of this type of contact is represented by C or directly omitted by C.
Changeover contacts:
A. Pins 85 and 86 are connected to the coil. If only pins 30 and 87 are connected and 87a is left empty, the usage is the same as that of a normally open contact;
B. If you only connect pins 30 and 87a, and leave 87 empty, it will become a normally closed contact relay. The working principle is opposite to that of normally open, that is: when the coil reaches the disconnect voltage, the contact is disconnected and the load stops working;
C. In order to combine into a circuit, the pins of the three contacts can be connected to achieve different functions. Generally, it is used in combination of multiple channels. This method of use is common in twin relays.