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Signs of a Bad Relay Switch – 5 Reliable Checks To Make


Signs of a Bad Relay Switch – 5 Reliable Checks To Make

Your car is acting strangely and you don’t understand why. Since many car problems often have some of the same symptoms, it’s important to know how to distinguish things like a bad relay switch from other possible issues. 

Signs of a bad relay switch include engine stalls, engine not starting, dead battery in the mornings, erratic dashboard lights, and an electric smell. Those experiencing several of these problems should look to a bad relay switch as the cause. 

Read on to get further information on relay switches, what they do, and how to know when they’ve gone bad. 

What Is An Ignition Relay Switch?

fuse and relay location

The ignition relay switch works to transmit power to your car’s fuel system. It activates when you turn the key in the ignition. The relay allows all systems to be powered and that includes allowing the battery to move power to the ignition coil, which then goes to the spark plugs to create fire to start the engine. 

The relay is typically located in or near the fuse box. The fuse box is either under the dashboard or the hood. It is typically yellow and you will know what it is because it contains many fuses. 

The relay box is usually black. The relay switches are located together and most are black although they can be white or some other color. They will be different sizes and have different parts numbers on them. 

You will likely need to look in your owner’s manual to see which relay goes to what car function. There is typically a diagram. 

The exact location of the ignition relay can be different depending on the make and model of the vehicle. Your service manual should have the exact location. 

A Look at Symptoms of a Bad Relay Switch

This is one of the most important and common symptoms of a bad ignition relay switch. A car that stalls during driving is unusual and only points to a few things. A burned-out ignition relay switch will cut power to the engine. This is why it stalls. 

This isn’t just the most common problem with a failed ignition relay switch. It is the most dangerous symptom as well as your car suddenly loses power. 

There are other symptoms that usually appear before this one so pay attention to the small clues before this major event happens.

Read: 5 Reasons Why A Car Engine Knocks On Startup Then Goes Away

A bad relay will cut power so your vehicle may not start. This is indicated by no lights and no electronics working on the dash. Nothing happens when you turn the key. There is no clicking or other sound and the car is just dead. That could also be a bad battery, so you will need to check your battery first and try jumping it off. 

Failure to jump off is a sure sign of a bad ignition relay switch. Most batteries, even older ones will dump off pretty easily. 

It’s best to have your battery checked anyway to rule out that possibility and test your ignition relay switch also.

signs of a bad relay switch no continuity

Read: How Long Can a Car Battery Sit Unused?

Another key symptom of a bad ignition relay switch is your battery chronically being dead in the morning. The reason for this is that a bad relay switch can leave your system constantly activated, even after you’ve turned it off. 

That means your battery is getting drained overnight. 

First, check to make sure your battery is good. You can have it tested for free at most auto retail shops.

Assuming your battery is good, you probably have a bad ignition relay switch. 

Testing a relay switch is simple enough with a multimeter. Those are also available at auto parts stores.

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measuring continuity

Read: Does a Car Battery Drain Faster In Cold?

A dashboard that lights up and blinks like an airport runway may indicate a bad ignition relay. Typically, there is corrosion inside the relay and there isn’t enough solid connection space. That causes your ignition to either go super fast or shut off. 

The light show usually happens when you start up your car but some could pop up while driving too. Be sure to have the relay switch checked soon if it does.

erratic dashboard lights

Ignition relays can rust, collect corrosion or accumulate water inside. This causes heat and sometimes causes the switch or the plastic cover to melt or burn. An electronic burned smell is a sure sign of a bad ignition relay switch. 

Besides the bad smell, a bad relay switch could eventually destroy your electrical system so take your vehicle to a mechanic immediately if you start smelling a burned odor. 

Read: Why Car Won’t Start in the Cold?


What happens when you have a bad relay switch?

Your engine likely will not turn over because the battery will not get the signal from the ignition switch. Jumping it off will not help. While it may appear to be the battery, it is more likely to be the ignition relay switch.

What causes a relay switch to go bad?

It could be any number of things. It could be a faulty circuit or contact fused or the relay may just be old. Most often, it’s corroded contacts. 

Corroded contacts limit the space for connectively, therefore causing the part to fail

How much does it cost to replace an ignition relay switch?

The cost to replace an ignition relay switch ranges between $50 and $75, with the parts costing around $20 and the labor between $30 and $55. It’s easy for someone to replace with a switch and no special tools are needed. Many people can do it themselves with some knowledge. 

Can you test a relay switch?

Yes, but you will need a multimeter to do it. Turn the multimeter to resistance and attach the probes to test for continuity. You want it to be in the 80s, depending on the model.

Can a bad relay cause a short in my car?

A relay that is damaged can cause the wiring to melt or a burning smell. A power surge can damage the electric system in your car. Don’t modify the relay as that can also damage your car. Replace it if it’s bad. 

Are they more than one relay switch?

There are different types of relay switches in your vehicle. There is the ignition relay, a horn relay, and a fuel pump relay among others. All work basically the same way but are built differently and are not always interchangeable. They can be interchangeable if they have the same parts number on them.

Can I test a relay without a multimeter?

Maybe. A car that won’t start and has a bad relay switch can be temporarily fixed by switching out the ignition relay with another relay switch on your vehicle that has the same part number on it. Make sure it is the same part.

Some cars use the same type of relay for several other things, like the horn or some other minor part. If that solves your problem, go to the parts store and buy another relay switch to replace the bad one. 

What’s the difference between an ignition relay and a starter relay?

The terms “starter relay” and “ignition relay” are used synonymously when talking about your average vehicle. It is a part of the ignition system that transfers power from the ignition switch to the starter motor.

Just be sure not to confuse it with the starter solenoid. Though the two behave similarly in operation, the solenoid is much larger and carries the full current from the battery to the starter motor.

Final Thoughts

Now that you know the signs of a bad relay switch, you can better evaluate whether or not that is your problem.

Remember that a bad relay can operate intermittently when it is in the process of failing. This can make it especially difficult to track down as the culprit!

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