So, automotive relays, are basically electrical switches, but without the on/off button.

They are used, to provide on/off functions, for many modern electrical features.

Relays in general are used to, enable a low amperage circuit, to switch on or off a higher amperage circuit.

There are several benefits of using automotive relays in a car. Firstly, using a relay means the switching circuit; does not require, a high current rated switch or cable, which reduces cost and weight.

Secondly, relays can be located, anywhere in the vehicle; to provide efficient power transfer, to the electrical accessory you are controlling. That’s why, relays are perfect for controlling many circuits in a car like; headlights, electric motors, fuel pumps, engine cooling fans, etc.

However, the real benefit behind a relay, is more than just automation. For example, they also provide the ability, to switch multiple circuits; including different voltage types, within the same automotive relays, at the same time. 12V DC relay switches, are the best solution for, full voltage applications.

Because, they allow, a low current flow circuit to control, a high current flow circuit, Like:

How Do They Work ?

Most automotive relays that you will see are either Single-Pole, Single-Throw (SPST) or Single-Pole; Double-Throw (SPDT) and draw very little current (less than 200 milliamps). They have either normally closed or normally open contacts, that will handle up to 30 or 40 amps and operate; using a control circuit that has the coil and a load circuit which has the switch. When power is applied to the coil, a magnetic field is created which either opens or closes the switch.

To test, use the following troubleshooting steps:

  1. Check for voltage at the point where the automotive relays plug in.
  2. If there is none, check the fuse or switch for defects. Also, check if there is voltage at the connection point, use the continuity function on the multimeter; to ensure a good ground connection on the opposite side of the relay.
  3. If Steps 1 and 2 do not reveal the source of the problem; check the voltage at the point where the relay connects to the battery or other power source. If there is no voltage here, there may be a problem with a fuse or circuit breaker.
  4. Finally, ensure that a proper connection exists, between the relay and the component; by using the continuity function of the multimeter. If the connection exists, and if the prior steps did not suggest another malfunction; then it may be time to replace the relay.

Choose Your Automotive Relays Help Topic Below

Cooling Fan Relay – What Does It Do – Failure Symptoms – Basic Testing

Automatic Shutdown (ASD) Relay – Function – Failure – Testing

Fuel Pump Relay – Function And Testing Procedures


Thank You !