Automotive Relays, How They Work, and Their Types

Modern automobiles feature countless electrical systems, such as the horn, headlights, fan motors, and auxiliary lamps. Obviously, all these systems need power, and that power needs to be regulated and controlled. This is where relays come in. Relay switches controlled by electrical power, with the purpose of automating this power to switch electrical circuits on and off at particular times. Relays can also switch multiple circuits, including different voltage types, within the same relay at the same time.

Automotive Relays consist of an electromagnetic coil, a switch, and a spring. The spring holds the switch in position until a current is passed through the coil, which then generates the magnetic field which moves the switch on and off.

Various applications require various types of relays. The most common types of relays include:

  • Change Over Relays: The most common types of relays, with five pins that can be wired to normally open using pins 30 and 87, normally closed using pins 30 and 87a, or wired as a changeover using pin 30 and both 87 and 87a. When being used as a changeover, the relay switches current from one circuit to another and back again, depending on the coil’s states.
  • Normally Open relays specifically only have four pins, which means they can only be wired one way, normally open.
  • Potted relays are like any other relay, except they are sealed with epoxy to create a watertight enclosure.
  • Flasher relays have two or three pins as opposed to the standard four or five. They are used primarily for lights in cars, with multiple types of flashers existing for various purposes, such as LED lights, wigwags, and thermally controlled relays.
  • Skirted relays have an extended skirt around the bottom to seal away water and contaminants from the contacts.
  • Time delay relays are adjustable to maintain the current flow through the contacts. Duration of the current flow can be adjusted from two seconds up to three minutes after power is switched off to the coil. The relay contains a solid-state circuit with variable resistor that controls the time delay setting. Time delay relays are often used for powering vehicle parking lights for an extended time after the driver exits the vehicle to be able to see around it.
  • Dual open contact relays have five pins like a changeover but have a dual set of contacts instead of a single contact.

At Veritable Aerospace, owned and operated by ASAP Semiconductor, we can help you find all the connector relays for the aerospace, automotive, and defense industries. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, email us at sales@veritableaerospace.com or call us at 1-714-705-4780.


  1. Posted on July 23, 2019
  2. connectors

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