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No matter what car you drive, all vehicles have one thing in common — they all face electrical issues at some point. So, why don’t you learn how to test a relay with a multimeter? It is a valuable skill to have under the belt.
Back in the day, vehicles didn’t have fuse boxes, and so they relied on a single computer. This, of course, was incredibly expensive. Testing a relay was hard work.
But it’s all in the past now. In the modern age, you can now test a relay in a few pretty easy steps.
How Does a Relay Diagram Work?
Before testing a relay, you must understand how it works behind the scenes. For example, if you remove the relay from the fuse box, you’ll notice that it has a weird-looking diagram along with some numbers.
Those numbers or pins control different things in your relay. For example, a 4-pin relay uses pin 85, 86, 30, and 87. Notice that they are spawned across the relay for the sake of convenience.
Pins 85 and 86, which are parallel to each other, control the coil and two pins. On the other hand, 30 and 87 turn on the switch power when the coil kicks in.
There are also 5-pin relays, and although they are pretty similar, they have some subtitle differences. For instance, pins 85 and 86 control the coil and three pins. The 30, 87, and 87A switch the power between different circuits.
But in some cases, your relay might not have any numbers on the side. Instead, it’ll have numbers labeled on top.
You should also know that the diagram on your relay can change depending on your vehicle. Still, it’s easy to comprehend what each pin is doing if you know the basics.
How to Test a Relay Using a Multimeter
Not sure how to test a relay switch with a multimeter? We got you. Follow these simple steps to know more:
What You Will Need
Get all these tools for this job:
- A jumper box — to make sure that the coil is kicking, you have to power the relay. As an alternative, use your car’s battery as a source of power.
- A multimeter — to determine if the relay has resistance, you must use a multimeter.
1. Test the Coil on Pins 85 & 86
To start, we’ll test the coil of the relay. However, keep in mind that this is just a bench test. We’re not testing the relay on the vehicle.
That being said, set the multimeter to the resistance setting. Next up, please grab both the red and black terminals and put them on pins 85 and 86. The multimeter will now pick up the OHMs and display them on screen.
2. Test Resistance on Pins 30 & 87
Here’s how to test a relay with a multimeter for pins 30 and 87: place the leads from the multimeter on the pins, and it will read the resistance.
However, you shouldn’t have any resistance on any of those pins. But if you do, the switch inside is stuck closed. You should only have resistance when the coil kicks in.
3. Add Power & Ground to Pins 85 & 86
After checking for resistance on pins 30 and 87, we have to energize the relay itself to see if the coil kicks in. As we said at the beginning, we’re just bench testing the relay. So, to verify that it works, we have to power the unit.
That said, get your jumper box and then connect the red lead from the jumper box to pin 85. Once that’s done, grab the black lead and hook it up to pin 86. If you can hear the coil kicking in, that means the solenoid is engaging, and so the relay is in great shape.
4. Check for Continuity
You still have some work ahead of you before determining if the relay is working. So, set the multimeter to continuity. After that, put the red lead from the jumper box on pin 85. Next up, place the red lead from the multimeter on pin 30 and the black one on pin 87.
Now take the ground from the power box, and place it on pin 86. Your multimeter should now beep, indicating that the relay has continuity and that it’s still in great shape.
For more information about relays, we suggest watching this video:
How to Test a Car’s Fuse Using a Multimeter
Don’t know how to test a relay fuse? Here’s how you can check it in a snap:
A) Configure the Multimeter
Before moving any further, please turn the wheel to the continuity option. Once that’s done, move onto the next section.
B) How to Test Fuses and Relays With a Multimeter
Once you’ve set the device to continuity, put the leads on both ends of the fuse. If you’re getting continuity, the multimeter will make some noise. That way, you’ll know for sure that the fuse is working.
Otherwise, look at the inside of the fuse. If it seems broken or blown, throw it away and get a new one.
Frequently Asked Questions (FAQs)
Need more information about relays? Here’s some info to clear up most questions most people have:
What is the best way to test a relay?
- One of the easiest ways to learn how to test a relay fuse with a multimeter is to use a power supply and a multimeter. Once you have those two things, you should run a test to find out if the coil kicks in when it gets power.
How many Ohms should a relay have?
- Unfortunately, there’s no definitive answer to this question since this is up to the manufacturer. However, on average, your relay should have about 50 to 200 ohms. For accurate information, refer to your owner’s manual.
Does a relay click when it’s damaged?
- Just because the relay clicks, it doesn’t mean it’s working. It just means that the coil is getting enough power to move. You still have to check that the pins 30 and 87 have continuity when the coil kicks in.
How can I tell if a car fuse is not working?
- If the inside of the fuse looks split in half, you got a blown fuse. Otherwise, use a multimeter to check the fuse.
Electrical problems are certainly not fun to deal with, but they cannot be ignored. So, it is crucial to learn how to test a relay with a multimeter on your own.
And even if you’re not fond of electricity or anything that requires a multimeter, you should be able to run a little test at home without going to the local mechanic. Sure, it takes a little bit of time, but you can save yourself some money doing it yourself.