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Electrical Relay Explained!

What is a Relay? its Applications, Functions, Parts, Diagram, Types, How it Works, Advantages, and Disadvantages

Relays are electrically operated switches designed for DC voltages in passenger comfort and retention systems, as well as controlling power levels in harsh environments.

These relays are operated by electrical power, a computer, or a control module and are used to automate the power to switch electrical circuits on and off at specific times. They can also switch multiple circuits, including different voltage types, within the same relay at the same time.

Applications of automotive relays include dashboard indicator lights, headlights, braking, trafficator lights, engine fans, windscreens, wipers, and almost all vehicle electrical systems.

These relays support modern electrical conveniences and safety features in vehicles, supporting all types of vehicles. 12V DC relay switches are suitable for full voltage applications, as a low current flow circuit can control a high current flow circuit, such as a vehicle’s horn, headlights, auxiliary lamps, fan motors, and blower motors.

Relays are electronic parts that exchange high voltages or currents with a lower voltage or current, functioning as a switch controlled by an electrical signal.

They open or close a circuit in response to signals, allowing or preventing current flow. Understanding the purpose of automotive relays is crucial as they save the life of many bigger electrical appliances in vehicles.

Relays are essential in vehicles, consisting of a frame, coil, armature, and contacts. These relays have two circuits: an energizing circuit and a contact circuit. The energizing side has the coil, while the relay contacts have the contact side.

In an AC unit, the polarity changes 120 times per second, while in a DC system, it is fixed.

There are various types of car relays to meet the requirements of various applications. Normally open relays have four pins and can be wired in one way, unlike changeover relays that can be wired into different forms.

Change over relays have five standard pins and can be wired as Normally Open (N.O.) or Normally Closed (N.C.). Dual open-contact relays have five pins but have a dual set of contacts instead of a single contact.

Potted relays are special relays that function like other types but are sealed with epoxy to prevent water penetration.

LED flashers are electrically controlled by a small solid-state integrated circuit board, designed to work with low current draw of LED lighting without causing issues.

Time delay relays are adjustable to maintain and control current flow through their contacts, with a duration of current flow ranging from 2 seconds to 3 minutes after power is switched off to the coil. Flasher relays have two or three pins, with some acting more like circuit breakers.

Thermal (standard) flashers are thermally controlled like a circuit breaker, with the number of lights connected determining its output performance. Electromechanical flashers work with a circuit board containing a capacitor, diodes, and a coil to create the same flash pattern as a standard flasher.

Wig-wag flashers use a solid-state flash circuit to alternate between two separate lamp circuits. Skirted relays have an extended skirt around their bottom to seal around a socket, preventing water and contaminants from entering the relay contacts.

Relays are used in various industries, allowing for the switching of AC and DC currents. They consist of an electromagnet coil, a switch, and a spring that holds the switch in place until a current passes through the coil.

The coil generates a magnetic field, causing the switch to turn on and off. The pinout of a typical 12V relay consists of coil pins 85 and 86, and switch pins 30, 87, and 87a. Relays can be set to be open or closed, and can be reversed for a normally open relay.

However, there are disadvantages to relays, such as being too big for small currents, not being able to switch rapidly like transistors, using more power due to the current flowing through the coil, and potentially requiring a transistor to switch the current for the relay’s coil.

Relay testing is a crucial process that requires careful handling and safety precautions. It is essential to avoid working with relays in areas with flammable or explosive gases, and to use the service manual instead of the owner’s manual when identifying and understanding the wiring system and relays in your car.

To test a relay, follow these steps:

1. Find the relay that needs testing, either under the dash or in the engine compartment. Check the electrical chapter and wiring diagram in your service manual if unclear about the location.

2. Replace the relay with a known-good replacement to test it quickly and easily. While the relay is disconnected, check and clean the connectors.

3. Set an Ohms multimeter to Ohms and measure resistance by touching the leads across the electromagnet coil pins. If the relay is out of range or open due to a faulty electromagnetic coil winding, it is time for a replacement relay.

4. Connect a 9-12 V battery to power the electromagnet coil. As the coil energises and shuts the switch, there should be an audible “click” from the relay.

5. Jump the battery positive to one switch terminal while the coil is still active. Connect a test light between the ground and the other switch terminal. Check the voltage of the relay at the switch and ensure proper resistance by disconnecting the positive jumper wire and energise the electromagnet coil.

Relay Video

FAQs

What causes relay failure?

Leaky contacts, cracked contacts, or significant size and position displacement are the main negatives. This will have an impact on the relay’s contact dependability. Typically, contact overheating, wear, and welding are the problems of contact parts.

Can bad relay drain batteries?

The ignition relay is essentially a switch for the power to the ignition system’s electrical components. Making sure electricity gets from the battery to the various components that require power is its responsibility. A defective relay will drain your battery and make it challenging to turn the ignition.

Can you test a main relay?

It’s rather easy to determine if your main relay is impacted. Just start the car and see if it keeps running. If so, the primary relay is working properly. The primary relay can be affected if the engine cuts out.

Related: Different Parts of A Car Explained!

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