Symptoms of a Bad Starter Relay and How to Troubleshoot?

Knowing the symptoms of a bad starter relay will save you from being stranded in the middle of nowhere. The starter relay is one of the essential and most overlooked components of the ignition system.

This critical ignition component is designed to direct current from the car battery to the starter solenoid, triggering the starter motor to turn the engine. This means it serves as a switch between the starter motor and the starter solenoid in a vehicle. 

Starter relay issues are not common. It rarely fails, but when it does, it might keep you stranded because your car won’t start. However, several factors can cause a starter relay to fail. They include lousy circuits, corroded circuits, bridged contacts, wet relays, or even over-aged relays. When your starter relay fails or starts going bad, you’ll notice some warning signs to alert you to fix it on time.

This article will discuss these signs at length and examine how to tell if the starter relay is bad. We’ll also discuss the functions, what causes them to fail, and how to fix or replace them.

What does a starter relay do?

A starter relay is an ignition system component specially designed to transmit power from the car battery to the starter solenoid. This implies it is a switch between the starter solenoid and the starter motor. 

It is solely designed to transmit current from the car battery to the starter properly. Most car owners and mechanics confuse starter relay with being starter solenoid. These are two different ignition system components.

The starter solenoid works as an actuating coil of a connector, which carries electrical current from the starter solenoid to the starter motor. Starter solenoids are designed to engage the starter pinion with the ring gear of an engine.

So, how do the starter relay, starter solenoid, and starter motor work together? When you insert your key into the ignition key to turn it on, it energies the starter relay, which transfers power to the starter solenoid, which transmits power to the starter motor. 

A starter relay sends small electric power to the starter solenoid when you turn on the ignition key, while the solenoid draws a large current directly from the car batteries. This causes the solenoid to transfer power to the starter motor, which in turn spins the flywheel. 

All modern starters follow this process. They rely on the starter relay to send power to the solenoid, engaging the starter to turn the flywheel. The starter relay plays a significant role in starting your car.

Symptoms of a bad starter relay

Like every other mechanical and electrical component in your vehicle, the starter relay displays some signs that show it’s failing before it finally stops. Some of these signs are the same as the symptoms of a bad starter solenoid, and some indicate a bad starter motor. This makes it difficult to find. Let’s look at these symptoms below.

Car won’t start

The most common sign of a faulty or failing starter relay is that your car won’t start when you try to start it. If you try starting your car and there’s no sign of starting or even a click, and your interior lights are bright, it may be an indication of a bad starter relay. 

The problem might be that your car starter relay fuse is blown. Regardless of how many times you try, the car will not start. However, if you hear a clicking sound when trying to start the vehicle, it could mean your starter relay has not gone bad completely.

In either case, you have to diagnose your ignition system, if you know your way around it. If not, contact a professional mechanic for a thorough check.

Starter relay that stays on even after engine have started

When you turn on your ignition switch, it sends an electrical current to the starter relay, which transfers the current to the starter solenoid. The solenoid sends the power to the starter motor, which rotates the flexplate to start the engine.

Turning off the ignition switch should work the opposite; both the starter solenoid and the motor should stop working. If it doesn’t work in this sequence and the relay stays on even after the engine has started, you have a bad or failing starter relay. It could be the relay is sending a steady current.

This usually occurs when the relay is touching somewhere or exposed to high electrical power. You need to diagnose and fix this problem immediately because it could damage the entire starter system. 

A series of rapid click from the starter

Starter relay clicks, but no crank shows the starter motor is not receiving enough electrical current from the relay to turn the engine. This is also a sign of low or dead battery. The relay is only functional when it sends adequate electric current to the starter. Less or high power could either damage the entire starter system or won’t start the vehicle, accompanied by an annoying clicking sound.

Both could be a result of a corroded or aged relay whose contact points are deteriorated. Repair only requires cleaning the contact points to ensure proper flow or changing an old relay. You can clean a corroded relay by scrapping the rusted surface with sandpaper or sand scraper. You may consider replacing the relay for better output.

Intermittent issues starting the car

There are times the engine won’t start unless you switch the ignition key on and off a couple of times. It is a sign of a bad starter relay, and it’s caused mainly by corrosions, dirt, debris, or extended exposure to heat. The corrosion and residue will reduce the flow of electrical current within the circuit. 

A starter relay is a simplified ignition system component that doesn’t contain many parts, and that’s why it rarely fails. But when it does, it has to do with electrical conductivity problems.

How do you troubleshoot a start relay?

The symptoms could be due to a bad alternator or a dead or failing battery that needs changing or replacement. To find the actual cost of the problem, you have to conduct some tests on starter relay circuitry. 

Do not panic! You can perform the test yourself. In the following few paragraphs, we’ll explain how to test a starter relay in a simplified way.

Diagnosing the starter relay is pretty easy due to its location. All you need is proper tools and, of course, knowledge. 

how to tell if starter relay fuse is bad

Needed materials:

Screwdrivers

Test lights

A piece of wire to act as a jumper

Wrenches and socket sets (in case you need to lose anything).

Testing the starter relay

Before starting the test, get a fully charged battery and a portable jumper cable. Or you can test your car battery and ensure it’s well-charged and not the cost of your problem. Be careful with the testing process and mind how you place the jumper cables on the battery terminals.

The testing procedures

Find the starter relay fuse location. The fuse location may vary from vehicle to vehicle. The fuses are majorly located close to the battery sitting with the positive battery terminal connected to it.

Have an assistant help you turn the ignition key to the ON position. If you hear a weak click sound, you’ll need to conduct an electrical resistance test. But if you hear an audible click, you need to diagnose the starter relay for voltage drop.

Diagnosing for electrical resistance

1). Get a test light, preferably a multimeter, and set it on the ohms scale. Contact one of the probes on the earth lead and the other on the ignition circuit terminal. A good starter relay should read below 5 ohms. Any reading above that indicates a defective relay.

2). The second method of diagnosing resistance is contacting the red multimeter probe to the ignition circuit wire and the other probe to the earth wire. If it reads less than 12V when you turn on the ignition switch, it indicates a faulty relay.

3). The third and final method of testing electrical resistance in our list is by using a portable jumper cable. Connect the battery lead and the ignition circuit lead. A strong click from the relay tells it’s working pretty fine. And a single or couple of weak clicks shows you have a faulty relay that needs a replacement.

Diagnosing for voltage drop

1). Reset your multimeter to be on 20V DC

2). Contact the red probe of the multimeter on the red terminal lead from the battery. Place the black and thin wire on the lead that goes to the ignition circuit lead switch. 

3). Tell your assistant to turn the ignition key to the ON position as you examine the multimeter reading. The voltage should not be above 0.2V. If the multimeter reads above 0.2V, either you have a bad starter relay or a problem with the electrical conductivity of the starter relay that needs proper attention. You have to check the connectors and clean them.

What causes a relay to fail?

Several factors can cause your car relay to fail, and they include;

Corrosion: Corroded leads or connectors cannot transfer the required amount of current. It will result in starting issues. It can be intermittent starting, a clicking noise from the relay, or an idle vehicle that cannot start.

Dirt and debris: This component is usually protected from dirt, debris, and grimes by placing them under the dashboard or hood. Over time, debris and dirt will accumulate and affect the functionality of the relay. As the dirt clump, it’ll not allow adequate flow of current, and you’ll hear a series of buzzing or clicking sounds from the relay.

Bad connectors: A defective or broken connector is a significant cause of a failed relay. The relay will not function properly if the required amount of current is not passing through. It will display some signs by giving a series of weak clicking sounds and unable to carry the starting circuits. Aside from the series of weak clicks, the vehicle may refuse to start.

Too much heat: If high voltage passes through the relay continually, it will generate excess heat that will burn or melt contacts causing them to stick together. This will close the starter circuit even when the ignition is off. This effect requires immediate attention because it can lead to damaging the entire starting system.

Overly aged relay: starter relay issues may not have any significant cause. It might be an overly-aged relay that has last hundreds of miles. An old relay may have a deteriorating part that can’t function properly. If this is the case, you need to replace the relay, Nothing more.

Now that you have known the symptoms and causes of a bad starter relay, how do you fix it? The answer depends on the cause of the failure. If it is caused by dirt or debris, cleaning them will be the best option. And if it is caused by excess heat or bad connectors, consider replacing them. That takes us to how to fix faulty starter relay problems.

how to test a starter relay

How to fix bad starter relay problems

If the relay failed due to corrosion or dirt on the leads, cleaning the connectors will restore the relay. You might need to inspect and clean the internal construction of the relay box. Depending on how dirty or corroded the connectors are, you may only need to clean the external parts. Cleaning the dirt and grimes requires a wire brush and baking powder. You may also need a blower and a microfiber towel for the cleaning process. 

Regardless of the cause, the best option for fixing a starter relay problem is to replace the relay. Replacing the relay means solving the problem once and for all. The starter relay is a long-lasting component that can last up to 100,000 miles. So replacing it is worth the cost. Let’s explore the processes involved.

Replacing a bad starting relay

Starter relay replacement is a pretty easy and quick fix. There are several processes to follow when installing a new starter relay. It all depends on the type of relay you’re replacing. 

How to safely remove a starter relay

Fuse box starter relay

Step 1: Raise the hood and disconnect the negative battery terminal with a sizeable wrench. 

Step 2: Find the fuse box. It is usually a black lid box located near the battery. If you’re finding it difficult to identify it, consult your owner’s booklet. The booklet will help you locate the starter relay.

Step 3: Disconnect the relay.

Fender wall relay

This starter relay is directly mounted on the firewall or fender. Follow the below steps to remove it.

Step 1: Disconnect the battery terminal using a sizable wrench.

Step 2: Disconnect the leads that go to the relay terminals. Use a matchable wrench or socket to loosen nuts that hold the relay leads.

Step 3: Take off the mounting screws that hold the relay to the fender. 

Installing a starter relay

Installing a fuse box starter relay is one of the most straightforward DIY jobs. There are no bolts, screws, nor nuts too tight – and nothing to worry about. Compare both new and old relay. Once you’re sure they’re the same, take the new relay and match the pins on their slots in the fuse box. Gently push it down until it gets to the end of the slot and seats evenly. Cover the fuse box and reconnect the battery terminals.

Follow the below steps to mount a fender wall relay; 

Place and hold the relay against the installation point. Plugin the screws and tighten them to hold the relay. Connect the starter circuit leads to the battery terminals. Ensure you connect the right wire to the right post. 

After installation, give yourself proof of doubt and recheck the work. Ensure the cables and connectors are intact on the fender wall relay. Test the starting system. If everything works, pat yourself on the back. However, if you’re not the DIY type and not comfortable with this guide, do not hesitate to seek professional assistance.

FAQS:

Does a relay click when it’s bad?

If you have a failing or bad starter relay, it will not provide adequate electrical current to power the starter motor. As a result, regardless of how many times you revolve the engine, it’ll not start. A defective starter relay will produce a click sound when you turn on the ignition.

Where is the starter relay switch located?

Starter relays are usually mounted on the engine bay but not on the engine block. You can track down the fuse box starter relay by following the big wire from the positive battery terminal. They are located close to the battery sitting in a box with a black lid on most vehicles.

How do you check if a starter relay is working?

The only tool required in checking a starter relay is a multimeter. Get a multimeter and set it on an ohms scale. Place one of the probes on the ground cable and the other probe on the ignition circuit terminal. 

A good relay should be under 5 ohms. If the readings go above 5 ohms, it shows you have a bad starter relay that needs replacement.

Final Thoughts

It is critical to ensure that the starter relay is functioning properly. Consider it as part of your car’s regular maintenance practices. Hence, knowing the symptoms of a bad starter relay and how to fix it will save you from getting stranded in the middle of nowhere.

I believe this article has guided you on the information and processes you need to fix your starter relay problems. You now know the functions, causes, and signs of a starter relay. You can diagnose, fix, or replace a bad starter relay.

Osuagwu Solomon

Osuagwu Solomon is a seasoned automotive technician for the past 9 years, and a technical writer. He loves writing about auto professional repair guides, DIY repair guides, and buyer’s guide. After spending six years in the automotive workshop, he decided to impact his knowledge to people aside his domain, and he has achieved this by centering his Automotive writing skills on REPAIRS.

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