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How to Test a Relay Without a Multimeter? 3 Easy Methods

By Arslan Ash

How to test a relay without a multimeter

As an electrical engineer, I love explaining how things like circuits and electronics work. I write on my blog to share simple explanations, reviews, and useful tips about the latest technology.

Relays are everywhere from your car to your washroom lights. So in my opinion one should know how to test a relay without a multimeter. As we all know, not everyone carries a multimeter all the time. Almost every single relay works on the same principle, you will give it the supply and it will open or close one or more circuits. To understand the troubleshooting of relays car is the best example.

Relays control different types of electrical functions in your car, such as sensors, switches, locks, lights, fuel pumps, and fans. But before everything you should know how this damn thing works.

Basic Funtioing of a Relay

Basic Funtioing of a Relay

There are multiple types of relays but the basic functionality of all the relays is same. You have to give supply volatages to make the relay operational. As a result there will be one or more points will make or break connections as per relay type. Mainly there are two types of connections. Normally Open (NO) and normally Closed (NC) connections. 


How to Test a Relay Without a Multimeter?

If you don’t have multimeter then you can use three methods for testing relay including visual inspection, bypassing, and listening click. I will guide you these three methods one by one.

Method 1: Visual Inspection of Relay

Visual inspection is the first method of checking relays without a multimeter. Using this method, you can check the condition of your relay. 

Step#1 Inspect the Relay's Physical Condition

how to check car relay without a multimeter

Start by examining the relay's physical condition. Pay close attention to any signs of wear or damage on the relay. Look for discoloration, melting, or corrosion on the terminals. You may have a problem with the relay if you notice any of these issues. Corroded or burnt terminals, for instance, are clear signs of trouble.

Step#2 Listen for the Audible Click

You should also listen for an audible click when the relay is energized. You should hear a distinct clicking sound when you activate the relay (typically by turning on the associated component, such as the headlights). It indicates that the electromagnetic coil inside the relay is engaged and working properly. It is possible that a malfunction is occurring if you do not hear the click.

Step#3 Check for Loose Wires or Connections

How To Check for Loose Wires or Connections

Relay wires and connections should be secured. If the relay's connections are poor or the wires are loose, its performance may be affected. Gently wiggle the wires to see if they are firmly connected. In the event that you find any loose or disconnected wires, you should fix them as soon as possible.

Step#4  Note the Relay's Location and Purpose

how to locate car relay

Identify the relay's location within the vehicle's electrical system, as well as its purpose. It is valuable information to have when diagnosing a problem. Finding out which relay controls a malfunctioning component can help you pinpoint the issue quickly.

Step#5 Inspect Other Nearby Components

Inspect Other Nearby Components of relay

As you inspect the relay, make sure to check other nearby components as well. Problems with neighboring parts can sometimes mimic relay problems. 

Method 2: Bypassing The Relay

Bypassing the relay is easy method for checking the honesty of relay. Take the step by step guide:

Step#1 Gather the Necessary Tools

There are a few basic tools you will need to perform a bypass test. A jumper cable or a short piece of wire is the primary tool. By temporarily bypassing the control circuit of the relay, this wire will serve as a bridge. Typically, you can find the relay's control wiring diagram in the vehicle's repair manual or online.

Step#2 Isolate the Relay

how to isolate the car relay

Locate the relay you wish to test and isolate it from the control circuit. The relay must be disconnected from any wires or connectors currently connected. During this procedure, make sure there is no power running through the relay.

Step#3 Connect the Control Side Terminals

how to Bypassing The Relay

The control side terminals of the relay should be connected with the wire or jumper cable. There are typically labels on the relay itself to indicate which terminals are on the control side. Generally, one terminal is for power (labeled "30"), one is for ground (labeled "85"), and one is for signal (labeled "86"). By connecting the power and ground terminals with the wire, you effectively bypass the control circuit.

Step#4 Listen for the Click

how to test relay of car

Connect the terminals on the control side of the relay and turn on the component or system it controls. If you're testing a relay for headlights, turn on the headlights. Watch for the audible click that signifies the relay's engagement. Generally, the control circuit is in good shape if you hear the click of the relay.

Step#5 Interpret the Results

It is straightforward to interpret the results of the bypass test. Relays that click when activated are likely in good working order. When you don't hear the click, it suggests a problem with the relay, the control circuit, or the associated component. It may be necessary for you to perform more extensive troubleshooting in this situation.

Method 3: Listening Test

Most easy method for checking relay without multimeter is listening test. I will guide you step step by here.

Step#1 Prepare the Necessary Tools

As such there is no tool needed for this test. But still you need a noose plier or a screw driver to put out the relay from base. 

Step#2 Locate the Relay

Make sure you identify the specific relay you are testing. You must know which relay controls the component you're interested in, whether it's the fuel pump, radiator fan, or headlights. The best practice is to put one relay at a time and see what changes you saw in your vehicle.

Step#3 Place the Tool on the Relay

Once the relay is in place and the relevant component (e.g., headlights) is turned on, gently place the screwdriver or stethoscope's metal end on the relay's housing. To prevent electrical shocks or damage, do not touch any other components or electrical connections.

Step#4 Activate the Component

Turn on the system or component that the relay controls. Suppose you were testing a relay for a radiator fan. Turn the fan on while you do so. Now listen intently while the component engages. 

Step#5 Listen for the Audible Click

The listening test is designed to detect an audible click inside the relay. When the relay is functioning properly, you should hear a distinct click as it activates and switches the connected component on or off. Relay electromagnetic coils work as intended when this click occurs.

Step#6 Interpret the Results

It is straightforward to interpret the results. When the relay clicks, it indicates that it is in good working condition. No click may indicate a relay malfunction, possibly caused by an internal problem or an issue with the control circuit.


Safety Precautions

Safety is paramount when working on automotive electrical systems to avoid accidents, injuries, and vehicle damage. Take safety first before knowing how to test a relay without a multimeter..

Disconnecting the Battery

It is first necessary to disconnect the vehicle's battery before beginning any electrical work. Keeping this in mind is crucial to preventing accidents like short circuits and electrical shocks. When you test the relay or related components, disconnect the battery to prevent power from running through the circuits. Negative terminals should always be removed first, followed by positive terminals.

Wearing Safety Gear

When working on automotive electrical systems, it is necessary to handle sharp or hot tools and components. Wearing safety gear, such as gloves and safety glasses, is a good idea. Using these is a safe way to handle wires, relays, and other electrical components. Additionally, wearing appropriate clothing can prevent cuts and burns.

Handling Tools Carefully

During relay testing, it's important to handle tools carefully. It is important to use tools properly and to avoid mishandling them, which can result in accidents. You should maintain good working conditions for your tools in order to prevent accidents.

Working in a Well-Ventilated Area

There are many relay tests that require working with electrical systems that emit noxious gases or fumes. Well-ventilated areas are vital for preventing inhalation of harmful substances. A properly ventilated area helps disperse potentially hazardous gases, ensuring the safety and health of those performing the tests.

Avoiding Open Flames

Whenever working on automotive electrical systems, open flames, such as cigarettes or lighters, should be avoided. It is possible for gases from the battery or other electrical components to be flammable. There can be serious safety hazards associated with smoking or using an open flame near your work area. The best way to prevent accidents is to be cautious.

Properly Securing the Vehicle

It is important to secure the vehicle before performing any electrical work to avoid unexpected movement or rolling. The vehicle should be kept stationary during the testing process by using wheel chocks or a parking brake. As a result of this precaution, a safe work environment is maintained and accidents caused by vehicle movement are prevented.


Ending-Up

In the absence of a multimeter, knowing how to test a relay without a multimeter is a valuable skill. Safety should be your top priority when testing car relay. You can easily check your relay with visual inspection. Testing a relay is easy with bypass and listening click methods.