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Symptoms of a Bad Starter Relay and How to Test it?

Author: Apogeeweb
Date: 25 Aug 2021
test starter relay


Ⅰ Introduction

Ⅱ Function of Starter Relays

Ⅲ How does a Starter Relay Work with Others?

Ⅳ Location of Starter Relays

Ⅴ Symptoms of a Bad Starter Relay

5.1 the Vehicle doesn’t Start

5.2 Starter Relay Remains on after Engine Started

5.3 Starter Makes a Clicking Sound

5.4 Vehicle Starts to Intermit

Ⅵ How to Test a Starter Relay?

Ⅶ How To Replace A Starter Relay?

7.1 How to Remove a Starter Relay Correctly?

7.2 How to Install Starter Relays?

7.3 How to Wire Starter Relays?

Ⅷ Conclusion

Ⅸ Frequently Asked Questions about a Starter Relay


Before your engine turns over and starts, a sequence of steps takes place when you get inside and start your vehicle. The starter relay is one of the most crucial and often overlooked – components of any vehicle's ignition system. A starter relay is a small electrical device located in the high-current motor's starting circuit. A relay is simply a remote switch that regulates the current in a high-current circuit. A starter relay in a car uses the modest ignition switch current to close the considerably more powerful starter circuit.


The starter relay and the starter solenoid work together to run the starting mechanism in several automobile applications. In some cases, the ignition switch directly controls the starter solenoid circuit. These are often small vehicles with starting motors that do not require a lot of currents to operate.


In this article, you will find all there is to learn about the starter relay: its function, its location in a vehicle and how it works. We also included information about the signs of a bad starter relay, how to test it, and how to replace or fix a bad one. keep reading.


Video. How to Test Symptoms of a Bad Starter Relay


 Function of Starter Relays

Between the vehicle's battery and the starter motor, a starter relay serves as an electrical circuit completer or circuit breaker. It assists in increasing the battery's current so that less current is required upon ignition. It's a switch between the starter solenoid and the starter motor, according to this description.


When you turn the ignition key or push the start button on your car, it permits a large current to flow. The starter motor requires a considerable current, which the ignition switch cannot manage. It would burn out if it didn't have the relay.


It is possible that if the starter relay fails, the vehicle will not start. As we'll see later, there are a variety of reasons why this component can fail. They also necessitate various treatments based on the nature and severity of the harm. Some can be repaired, and others require the installation of a new relay.


Ⅲ How does a Starter Relay Work with Others?

How does a starter relay work?

Figure 1. How does a starter relay work?


When you turn on the ignition, your key activates the starter relay, which sends power to the starter solenoid, which then sends power to the starter motor.


When you switch on the ignition key, a starter relay transmits small electric power to the starter solenoid, while the solenoid pulls a big current straight from the car batteries. This activates the solenoid, which sends electricity to the starter motor, which spins the flywheel.


This procedure is followed by all modern starters. The starter relay is responsible for sending electricity to the solenoid, which engages the starter and turns the flywheel. When it comes to starting your car, the starter relay is crucial.


Location of Starter Relays

Location of Starter Relays

Figure 2. Location of Starter Relays


The position of the starter relay varies by vehicle type and model. The fuse box (also known as a power box), the fuse panel under the dash, or the right fender are all possible locations. It'll be under the hood, inside the large box with the black cover, in most autos. This is where a vehicle's fuses and relays are mounted, and it's also known as the fuse box. The box is normally mounted on the driver's side of the vehicle.


Wires are coming in and out of the relay. However, many other relays in the car have a similar appearance. A starter relay that is mounted in the fuse box under the dashboard may be hard to find or even remove. It may not be difficult to locate starter relays that attach to the fender wall. These relays, which are usually of the cylinder type, can be identified by their mounting posts and leads. Refer to your repair handbook if you're not sure which one is the starter relay.


 Symptoms of a Bad Starter Relay

The starter relay, like every other mechanical and electrical component in your vehicle, shows indicators of failure before finally stopping. Some of the signs of a damaged or worn-out starter relay are listed below. If you see these warning signs, schedule an appointment with a local ASE-certified mechanic to have your car thoroughly inspected, as these symptoms could suggest issues with other components.


The starter solenoid and the motor should both stop working when we turn off the ignition switch. The main contacts in the starter relay have most likely welded together in the closed position if it doesn't operate in this sequence and the relay stays on even after the engine has started. If this happens, the starter relay will become trapped in the on position, causing damage to the starter, circuit, relay, and transmission flywheel if not treated instantly.

Symptoms of a Bad Starter Relay

Figure 3. Symptoms of a Bad Starter Relay


5.1 the Vehicle doesnt Start

A car that just won't start is one of the most telling indications of car trouble. While a multitude of underlying faults can prevent a car from starting, a defective starter relay is frequently at the root of the issue. To understand why you must first gain a better knowledge of the starter relay's function.


When you turn the key in the ignition, your battery is jolted into action, releasing a burst of electrical energy. The starter motor is triggered by this energy and turns your engine over. However, before reaching the starter motor, the electrical impulse must first pass via the starter relay. The starter relay not only completes the electrical circuit but also increases the current from the battery.


If your starter relay fails, the electrical signal from the battery to the starter motor will never reach it. As a result, no matter how many times you turn the key, your engine will not start. When you turn the key, you may hear a clicking noise if the circuit hasn't broken. In either situation, you should get professional assistance to evaluate the symptom and precisely diagnose the cause.

5.2 Starter Relay Remains on after Engine Started

When you turn on your ignition, an electrical current is sent to the starter relay, which then passes it on to the starter solenoid. The starter motor rotates the flexplate to start the engine, and the solenoid supplies power to it.


The starter solenoid and the motor should both stop working when we turn off the ignition switch. The main contacts in the starter relay have most likely welded together in the closed position if it doesn't operate in this sequence and the relay stays on even after the engine has started. If this happens, the starter relay will become trapped in the on position, causing damage to the starter, circuit, relay, and transmission flywheel if not treated instantly.


It usually happens when the relay comes into contact with anything or is exposed to a lot of electricity. Because this problem has the potential to harm the entire starting system, you must diagnose and treat it right away.


5.3 Starter Makes a Clicking Sound

The relay usually functions on an all-or-nothing basis. Either it will send the entire electrical current, or it will not send anything at all. When the starter relay is destroyed, however, only a portion of the signal may be sent.


The starter relay clicks, but the engine does not turn, indicating that the starter motor is not receiving enough electrical current from the relay. This can also be an indication of a low or dead battery. Only when it transmits enough electric current to the starter is the relay functioning. Lesser high power may harm the entire starter mechanism or cause the vehicle to not start, accompanied by an obnoxious clicking sound.


Both could be caused by a corroded or aging relay with damaged contact points. Cleaning the contact points to guarantee correct flow or replacing an old relay are the only two options for repair. Scrape the rusted surface with sandpaper or a sand scraper to clean a corroded relay. You may replace the relay for greater output, or you could contact a professional mechanic.

5.4 Vehicle Starts to Intermit

When the starter relay is functioning, it transmits power to the starter each time it is engaged. However, debris, grime, and high heat can taint this component. The corrosion and residue in the circuit will limit the flow of electrical current. The starter relay may be forced to work intermittently as a result of these circumstances.


A starter relay is a basic ignition system component with few moving elements, which is why it rarely fails. When it occurs, though, it is due to electrical conductivity issues. If the relay isn't faulty, there may be a damaged or corroded wire connection under the hood.


 How to Test a Starter Relay?

How to Test a Starter Relay?

Figure4.How to Test a Starter Relay?



1. a fully charged battery

2. a portable jumper cable

3. baking soda, water and a wire brush


safety glasses and golves 


Step 1

Make sure the car is parked safely and that the transmission is in neutral or park. When working under the hood, you don't want the vehicle to move forward by accident.


Step 2

Get a fully charged battery and a portable jumper cord before conducting the test. Alternatively, you can check your car battery to make sure it's fully charged and not the source of your problem. Pay attention to how you connect the jumper cables to the battery terminals throughout the testing process.


Step 3

Examine the terminals on the battery and the starter. Make sure they're clear of rust, oil, dirt, and debris. Disconnect the minus battery cable and set it aside before cleaning the corroded terminals. Remove the positive battery cable from the battery and set it to the side. Ensure that the cables do not come into contact with the battery terminals by accident. Using baking soda, water, and a wire brush, clean rusted terminals. Clean the starter terminals if necessary. Disconnect the battery cables if possible.


Step 4

The cables from the starter solenoid to the starter relay should be followed. On the relay, there are four terminals. The two smaller wires are utilized to turn the relay "On" and come from the key switch circuit. The two larger wires run from the battery to the starter, carrying battery voltage. Remove the wires from the starter relay and mark the two smaller wires so they can be reconnected appropriately. Connect one end of a jumper wire to the chassis ground. The other end should be connected to terminal 86.


Step 5

Connect the positive battery post with a jumper wire. It's fine to leave the jumper wire attached for a short period now that the battery connection to the starter has been severed. Measure the resistance between terminals 30 and 87 with a digital voltmeter. It should have a resistance of less than one ohm. The relay is not working if the resistance is more than one ohm. Replacing the relay is necessary.


 How To Replace A Starter Relay?

To the positive battery post, connect a jumper wire. It's okay to leave the jumper wire connected for a short time now that the battery connection to the starter has been disconnected. Between terminals 30 and 87, use a digital voltmeter to measure resistance. Less than one ohm of resistance is required. The starter relay will not work if the resistance is greater than one ohm. The relay must be changed.


Materials: safety glasses, safety wire

Tools: pliers, wrenches, and wires


7.1 How to Remove a Starter Relay Correctly?

You can open the hood and unhook the negative connection of the battery if it's a fuse box starter relay. Locate the fuse box next. It's usually the black-lidded box. Use the instructions if you can't find the starter relay. Determine the location of the starter relay using the information on the fuse box cover. Then, remove the starter relay.


If it's a fender wall relay, follow the methods below to get rid of it. To begin, detach the battery terminals with a wrench. Second, disconnect the leads that connect to the relay's terminals. Remove the bolts that attach the leads to the posts on the relay with a wrench. Two large and two little posts will serve as connection points. Third, remove the relay from the fender by unscrewing the mounting screws.

Remove a Starter Relay

 Figure6. Remove a Starter Relay


7.2 How to Install Starter Relays?

The process of installing a fuse box starter relay is simple. There are no nuts or screws to tighten, and there is no need to worry about torque.


Take your new relay with you. Push the relay in slowly and gently until it reaches the end of the seating, matching the pins with their slots in the fuse box. Replace the lid and reconnect the battery terminal that was detached when the old relay was removed.


Follow these procedures to install a fender-mounted starter relay.


Place the relay on the mounting surface and hold it there. Screw the relay to the fender wall by inserting and tightening the screws. Install the starter circuit and battery wires, being careful not to connect the wrong wire to the wrong post. Reconnect the battery cables that you have previously disconnected.

Install Starter Relays

Figure7. Install Starter Relays


Test the starting system once the installation is complete. The vehicle should start without difficulty. Check the wires and connections if this is the case. Make that the connections are secure and the fender wall starter relay is properly wired. If you can't figure out the problem, you need to look at the other components of the starting system. Alternatively, get the car inspected by a mechanic.


7.3 How to Wire Starter Relays?

Wires are installed on the connection posts of a fender-mounted starter relay. Typically, these leads are connected during the installation process. The relay must be wired appropriately to function safely. This diagram shows how to wire a four-connection starter relay.

How to Wire Starter Relays?

Figure8. How to Wire Starter Relays?



Disconnect the positive terminal of the battery. To avoid mishaps, secure the exposed end. You could do it using tape.



The thick starter solenoid cable can be found here. Connect it to one of the relay's large studs or posts. Tighten the mounting bolt to secure the connection. Because starter relays don't have polarity, it doesn't matter which big terminal you connect the wire to.



Obtain the wires for the ignition switch. They are usually thinner than starter cables since they only carry a limited quantity of current. One of the two wires should be connected to one of the small studs on the relay. Connect the remaining small post to the other wire.


There will be only one small post on some relays. Connect the ignition wires to the mounting screw or bolt if this is the case. It can also be connected to any other part of the relay housing. This is because one of the relay's tiny terminals is normally grounded.



Connect the remaining thick wire to the single huge stud or post that remains. This is the cable that connects to the battery's positive terminal.


Finally, turn on the ignition to test the relay wire. The engine should start and crank without difficulty. If it still doesn't work, double-check the wiring to make sure each cable is connected to the correct terminal and is securely fastened.



It's crucial to check that starter relays are functional in vehicles that require them. It is a standard aspect of a vehicle's routine maintenance. It can save you from getting into trouble and being stranded in the middle of nowhere. Knowing how the relay works and how to recognize a failed one early on is the first step.


We hope that this starter relay guide has provided you with enough knowledge to assist you in resolving starter relay problems that cause car starting problems. You can now recognize the signs of a malfunctioning starter relay, as well as how to test it.


 Frequently Asked Questions about a Starter Relay

1.Can you fix a starter relay?

If the starter relay fails, you won't be able to start the engine. Damage to the starter relay often happens from a bad power connection on the starter that causes it to short circuit. A nonworking relay cannot be dismantled for repair; you will have to install a new one in order to start the engine.


2.How easy is it to replace a starter relay?

With the right tools and knowledge of what wire to connect to which terminal, the process to change a starter relay should be easy. The fuse box relay is even easier. It usually involves pushing in the new relay after pulling out the old one.


3.What is the starter relay replacement cost?

Excluding the starter relay cost, expect to pay around $30. Adding the cost to buy the component, the total cost to install a new relay comes to about $50.


4.How long does a starter relay last?

Typically, expect a starter relay to last more than 100 miles. These components are durable, having only a few moving parts and, therefore, minimal wear. The biggest threat to a starter relays lifespan is usually the contacts burning out.


5.Is a starter relay the same as a starter solenoid?

Most often, a true starter relay is a small black cube plugged into an electrical fuse/relay box in the engine compartment, whereas a starter solenoid is (in most cases) attached directly to the starter on the engine (although it is sometimes located elsewhere in the engine compartment).



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