Relay Testing: A Comprehensive Guide

This blog post will discuss a comprehensive guide to relay testing. We will go over the importance of relay testing and provide an in-depth overview of how it works. You may not know what a relay is or why you should care about it, but you’ll be able to answer these questions after reading this article.

One of the essential aspects of relay testing is verifying that the relay will correctly turn on and off when it receives the correct control signal. You can do this using a multimeter or oscilloscope.

Your car has parts that power things in the car. These can be difficult to find when something is wrong. But with the electronics, it is easier because they are probably related to a relay.

Relays are used to turn your car’s electrical components on and off. These switches allow one circuit to control another even if the voltages are different. When a relay fails, it’s vital to know where the problem is so that it can be diagnosed and fixed without causing damage to the vehicle.

What Is Relay Diagnostics?

Time Required: It will take approximately one hour to an hour and a half, depending on experience and the relay site.

Level of Skill: Beginner

The Automobile System: Electrical

What Is A Relay, And How Does It Work?

A relay is a small switch that is used to turn on or off a higher power circuit. You can find them in many different vehicles, and they are also used in marine and aviation applications. They work by controlling the low amperage circuit, so it switches on or off the high amperage circuit.

Imagine your car’s headlights. If you connected the lights to the button in the car, then they would be on all the time. This can cause wires to melt and even cause a fire in some cases. Relays are used for when you want something like turning on your headlights when your wipers are turned on or when you want to extend an antenna when you turn on a radio.

Safety Relays

The relay test is a simple process, but you need to be safe about it. Be sure to do the following things when working with relays:

  • If you find that the relay is not working, do not get a new one from anywhere else. Get it from the same place, or you can hurt your car’s electrical systems.
  • You need to take care of the relay and not drop it. If the relay breaks, it could cause a fire or a wire to melt. Do not modify the relay at all.
  • Do not start working on a project with wires or anything that is electric in a space where there are any gases that can cause fire or explosions, such as gasoline or lighter fluid.
  • Even if you have plenty of experience, read the manual to understand the wiring.

All You’ll Need for a Relay Test

Checking your car’s relays is a straightforward procedure that doesn’t necessitate the use of a toolbox. To check for faulty relays, you need to prepare:

Standard Shop Tools:

  • high-impedance test light is a tool that can be used to look for problems with wires.
  • An ohmmeter is a tool that measures the resistance of a circuit. It is recommended that you have a vehicle service manual. But it is not required.

List of wires needed:

  • Wires with a metal core that can be used to simulate the jump in current between phases) – Jumper wires
  • A replacement relay is a part of an electrical system that can make it work when the old one doesn’t.

If you organize your tools and gear, then you will not need to wait a long time for them. You can get the sandpaper or blowtorch quickly. For this job, you do not need a blowtorch.

If you don’t have enough space in your garage, ask your town about working on your car outside. Some towns will say no. But if they say yes, make sure not to get any vehicles close to the street.

A Guide How to Test a Relay

Here’s how you start:

  1. Find the relay that you need to test. Depending on what it controls, it could be under the dashboard or in the engine bay. If you’re unsure where it is, check your owner’s manual and electrical wiring diagram for more information.
  2. If you want to test a relay, swap it with a known good one. The problem with this is that the first problem can happen again. And, if this happens, you have to buy more parts. If you do this, clean and inspect the connectors on the new part, so it works better.
  3. Get an Ohms multimeter. Touch the leads of the multimeter across the electromagnet coil pins, and see how much resistance you get. The amount should be between 50-120 ohms. If it isn’t, your relay is faulty, so repair or replace it if necessary.
  4. To measure the electric current, do these steps. Touch the lead to the switch pins. If it is a normally open relay, it will read OL or open.
  5. Put the battery across the pins. You should hear a clicking sound on the relay when it turns on and closes the switch. The polarity doesn’t matter on this 4-pin relay, but it does matter with diodes.
  6. With the battery positive still connected, touch it to one of the terminals. Connect a test light with the other terminal and ground. The test light should be drawing electricity and turned on. Take away your battery positive jumpers, and the test light should turn off.
  7. Test the relay’s voltage at the switch. If it is low, then there might be bad contact points. Remove the test light and set your multimeter to DC volts. Touch the leads across the pins or connectors of the test light. The reading should match that of your battery voltage.
  8. The first thing to do is turn off the power to the switch. Then you may measure a small amount of resistance. Next, you should measure the resistance across the pins on your switch. If it’s near-zero ohms, then it is open. If it has any resistance, then it’s closed.

Testing a Relay with These Tips

There are different types of car relays. They found that the best ones are the simplest.

Here are some tips from us professionals to make sure you buy the right car for your vehicle. It is good to know how to fix anything, but it’s best if you don’t try everything. Get a manual for your automobile at an auto parts store and check it regularly.

  • When you are not sure about a relay, just throw it away. If something is not working or seems like it might be broken, then replace it with another one. It may cost money to buy a new one, but it is better than getting something that is broken.
  • Make sure you have all of your tools ready before starting. This will help you not get distracted and forget something that you need to do. It’s called “mise en place,” which means that things are in their place. If you don’t have an ohmmeter or a test light, you can’t test relays. It’s to replace them, but it’ll be a guessing game as to whether or not the relay is defective without testing first.

Frequently Asked Questions about How to Test a Relay

What if I ignore the problem’s existence?

Ignoring a misbehaving relay can cause significant problems under your hood. This is because the relay could be making lousy electricity, and that could make wires get hot. If you have a faulty relay, then this will also make your car’s engine stop working, and there might even be a fire!

Is it possible to test relays without an ohmmeter or a test light?

No. If you are not sure if there is a problem with the relay, you can choose to replace it yourself or pay someone else to do the work.

What if my vehicle’s relays are difficult to find or hidden?

Most of the time, you should put your relay in a place where it is easy to get to. But if you are not sure about one, then it is best to have someone with experience check it out. It can hurt your knuckles and damage your suitable relays when you dig around blindly.

Is it true that all automobiles have relays?

Most new cars have relays. This is because vehicles now have many, many electronic devices and systems in them.

What Is The Average Cost To Test A Relay?

Testing and replacing a relay in your car can be expensive. That can cost from $5 to hundreds of dollars.

An ohmmeter can be bought for less than $20. There are different designs of this tool. A high-impedance test light costs more, usually between $20 and $40, but it does not matter if it is more expensive.

You can buy wire at many stores. It is cheap, but it depends on how long the length of the wire is.

How do you check if a relay is bad?

The tool you need to test a relay is a multimeter. First, remove the relay from the fuse box and measure DC voltage at 85 positions (or wherever your relay is).

How do you test a relay circuit?

You can test a relay by putting your multimeter in continuity mode. Check to see if the two poles are connected. If they are, there is no problem with the relay. If not, then there’s an issue with the relay, and you need to fix it before using it. Then when you turn on the power of the relay, check again for continuity between N/O contacts and pole to make sure that they are connected by electricity.

How do you test a relay with a test light?

The high impedance test light will show you if the relay is working. Connect the test lights to a suitable ground and touch it to the wire from the relay. If you see a bulb, then there should be power going through the wire.

How do you test a relay terminal?

Find the NO terminal of the relay. Put one probe of your multimeter on this terminal and another probe on the COM terminal. If the resistance is high, then it is working.