The electric fan can be turned on in two ways. The first is using an electromagnetic relay, and the second without it. But in any of these schemes, it will be useful to use the forced fan switch.
Instructions
Step 1
Cars use electric fans to blow the cooling system radiator. The fan is an impeller driven by a DC motor mounted in a round or square frame. The activation of the electric fan is fully automatic, depending on the temperature of the coolant in the radiator. Liquid temperature data is taken from a sensor installed in the side compartment of the radiator. The sensor is a simple microswitch with normally open contacts. They are closed when a certain temperature is reached.
Step 2
To connect an electric fan, you can use two schemes: relay and relayless. The difference between these schemes is evident from the name. The relayless circuit consists of a temperature sensor, a fan, a fuse, and connecting wires. The positive terminal of the electric fan is connected via a fuse to the positive terminal of the battery. The negative terminal of the fan is connected to any terminal of the temperature sensor; the polarity of the switch does not matter. The second output of the sensor must be connected to the car body. This is the simplest connection scheme, it does not take much time to implement.
Step 3
The relay circuit contains an electromechanical relay. The good thing is that the high current is removed from the sensor to the relay. The positive terminal of the fan is connected through a fuse to the battery, negative to the body. The negative wire must be cut and the resulting two wires must be connected to the normally open contacts of the relay. By default, our fan is turned off. One terminal of the relay coil must be powered from the positive of the battery through a fuse, or from the ignition switch. The second lead of the coil should be applied to the first contact of the temperature sensor, and from the second contact, mount the wire connected to the body. Check in advance if there is a diode in the relay connected in parallel with the coil. If so, it is important to observe the polarity of the winding supply.
Step 4
Another useful improvement for the fan switching circuit is a button installed in the car's interior. The temperature sensor can fail at the most inopportune moment, so the button will be useful for emergencies. Both when using the first circuit, and when using the second, you need to connect the normally open contacts of the button with the temperature sensor. It's easier this way, but in the case of using the first circuit, it turns out that there will be a large current on the button, and this can cause the button contacts to burn and melt the case. Therefore, it is best to use the button in a duet with an electromagnetic relay.
