Page 225 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

Role of solenoid switch and relay, Importance of checking

of Soleniod switch and Relay

Objectives: At the end of this lesson you shall be able to
• explain Role of solenoid switch and relay
• demonstrate importance of its checking solenoid and relay.

Solenoid switch: A solenoid is an electrochemical switch/ valve that is controlled by an electric current. The
electric current runs through a solenoid, which is a wire coil wrapped around a metallic core. A solenoid creates
a controlled magnetic field when an electrical current is passed through it. This magnetic field affects the state of
the solenoid valve, causing the valve to open or close.

Roll of solenoid switch: In automobiles, a solenoid switch plays a crucial role in starting the engine. It’s typically
part of the starter system, responsible for engaging the starter motor with the engine’s flywheel when the ignition
key is turned. Essentially, it acts as a relay, allowing high current to flow to the starter motor from the battery to
start the engine.
Importance of checking solenoid switch:

• Reliability: Make sure that solenoid switch is functioning properly helps maintain the reliability of the vehicle’s
starting system. A faulty solenoid switch can lead to starting problems.
• Safety: A malfunctioning solenoid switch can potentially cause electrical issues or even lead to a vehicle fire
in extreme cases. Regular checks help ensure safety on the road.
• Preventative maintenance: By checking the solenoid switch regularly, you can find out any issues early on,
preventing more significant and costly problems down the line.

• Extended lifespan: Proper maintenance and inspection can extend the life of a solenoid switch, reducing the
need for premature replacement.
• Performance: A well-functioning solenoid switch ensures smooth engine starting, which can contribute to the
vehicle’s overall efficiency and performance.
Relay: A relay is an electrically operated switch. many relays use an electromagnet to operate a switching
mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to
control a circuit by a low-power signal (with compete electrical isolation between control and controlled circuits),
or where several circuits must be controlled by one signal.

Types of relay:
• Normally open relay [NO]: Power circuit is in open position. Circuit closes when control circuit is activated.
• Normally close relay [NC]: Power circuit is in close position. Circuit opens when control circuit is activated.

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CITS : Automotive - Mechanic Diesel - Lesson 62 - 66