Ignition Relay vs Starter Relay: What’s the Difference?


Ignition Relay vs Starter Relay

Affiliate Disclaimer

As an affiliate, we may earn a commission from qualifying purchases. We get commissions for purchases made through links on this website from Amazon and other third parties.

When it comes to understanding the electrical system of your vehicle, there are certain components that play a crucial role in its operation.

Two such components are the ignition relay and starter relay. But what exactly is the difference between these two relays? Let’s find out the difference between Ignition Relay vs Starter Relay.

The ignition relay and starter relay may sound similar, but they have distinct functions in your car’s electrical system.

On the other hand, the starter relay is specifically designed to control one vital component the starter motor.

In this article about automotive electrical systems, we will dive deeper into each type of relays!

Ignition Relay vs Starter Relay:

Here is the difference between an ignition relay and a starter relay:

Ignition relays and starter relays are both electrical components that are used to control the flow of current in a car’s electrical system. However, they have different functions.

The ignition relay is used to control the power to the ignition coil. This coil is responsible for generating the spark that ignites the fuel in the engine. The ignition relay helps to protect the ignition coil from damage by preventing it from receiving too much current.

The starter relay is used to control the power to the starter motor. The starter motor is responsible for turning the engine over when the car is started. The starter relay helps to protect the starter motor from damage by preventing it from receiving too much current.

If either the ignition relay or the starter relay fails, the car will not start. If you are having trouble starting your car, it is a good idea to have both relays checked.

Here is a table that summarizes the key differences between ignition relays and starter relays:

FeatureIgnition RelayStarter Relay
FunctionControls power to ignition coilControls power to starter motor
LocationIn the fuse box or under the hoodIn the fuse box or under the hood
Symptoms of failureCar will not startCar will not start
Repair cost$20-50$20-50

What Is an Ignition Relay?

An ignition relay is a crucial component in the electrical system of a vehicle. It serves as a switch that controls the flow of electricity to various components involved in starting and running the engine.

Here are some key points to understand about ignition relays:

  1. Function: The primary function of an ignition relay is to provide power to the starter motor, which turns over the engine when you start your car. It acts as a bridge between the battery and the starter, allowing current to flow from one to another.
  2. Electrical Control: An ignition relay operates through an electromagnetic coil mechanism that responds to signals from your car’s ignition switch or key cylinder. When you turn on the ignition, it sends a low-voltage signal to activate the relay, which then closes its internal contacts and allows high-current flow.
  3. Safety Feature: Ignition relays play an important role in ensuring safety by preventing accidental starting or cranking of the engine while it’s already running or being serviced. They typically have built-in features like diodes or resistors that protect against voltage spikes or feedback.
  4. Location: In most vehicles, you can find the ignition relay mounted near other fuses and relays within either underhood fuse/relay boxes or interior fuse panels for easy access and maintenance.
  5. Testing & Replacement: If you suspect an issue with your vehicle’s starting system, testing and replacing an ignition relay may be necessary. Various symptoms such as no-start condition, intermittent starting problems, clicking sounds during startup can indicate potential issues with this component.

What Is a Starter Relay?

A starter relay, also known as a solenoid switch or starter solenoid, is an electrical device used in vehicles to control the flow of current from the battery to the starter motor.

It acts as a bridge between the ignition switch and the starter motor, allowing for efficient starting of the engine.

Here are some key points about what a starter relay does:

  1. Electromagnetic operation: The core function of a starter relay is to engage and disengage power to the starter motor using an electromagnetic coil. When you turn your ignition key or press the start button, it activates this coil, which pulls in contacts that allow electrical current from the battery to reach the starter motor.
  2. High-current switching: Starter motors require large amounts of electric current to function properly. A typical automotive relay can handle high currents without overheating or sustaining damage. This makes it an ideal component for controlling power delivery between your vehicle’s battery and its powerful starting system.
  3. Protection against continuous engagement: One crucial feature of a starter relay is that it prevents continuous engagement of the starter motor after your vehicle’s engine has started running. Once you release your ignition key or stop pressing on the start button, spring-loaded contacts within the relay quickly open up and disconnect power supply to prevent unnecessary wear on both components.
  4. Integration with other systems: In modern vehicles equipped with advanced electronics, starters relays often integrate with other systems such as anti-theft immobilizers or engine management units (ECUs). These integrations ensure proper coordination among various components during engine startup while providing additional security features.
  5. Common symptoms of failure: Like any electrical component, a faulty starter relay may exhibit certain warning signs when nearing failure or malfunctioning altogether: intermittent starting issues (clicking sound but no cranking), complete loss of power when attempting to start, or even constant engagement causing grinding noises.

Differences Between Ignition and Starter Relays:

When it comes to automotive electrical systems, the ignition relay and the starter relay are two vital components that serve different purposes.

Understanding their differences is crucial for maintaining a smooth functioning vehicle. Here’s a breakdown of how these relays differ:


  • The ignition relay is responsible for sending power to various electrical components in your vehicle, such as the fuel pump, engine control module (ECM), and ignition system.
  • On the other hand, the starter relay plays a critical role in starting your car’s engine by engaging the starter motor when you turn the key or press the start button.


  • Ignition relays are typically found within or near the fuse box of your vehicle.
  • Starter relays are usually located near or on top of the engine or attached directly to the starter motor itself.

Wiring Connections:

  • Ignition relays often have multiple connections since they need to distribute power to various components throughout your vehicle.
  • In contrast, starter relays generally have fewer connections as their primary purpose is to engage/disengage power supply from battery to starter motor.

Current Handling Capacity:

  • Ignition relays typically handle lower currents compared to starter relays because they only need enough current for powering electronic modules and accessories.
  • Starter relays, on the other hand, require higher current handling capacity due to their involvement in starting an internal combustion engine.

Operation Timing:

  • The ignition relay operates whenever you turn on your car’s electrical system; it remains active while driving and even after turning off your vehicle until certain conditions are met (e.g., door opening).
  • Conversely, a starter relay only activates momentarily during engine cranking when you initiate starting sequence through key-turning or button pressing.

Common Problems with Ignition and Starter Relays:

When it comes to ignition and starter relays, there are a few common problems that can occur. Here are some issues you may encounter:

  1. Relay Failure: Over time, relays can wear out or become damaged due to constant use or electrical faults. This can lead to the relay failing to function properly or not working at all.
  2. Electrical Shorts: If there are any short circuits in the wiring connected to the relay, it can cause damage and prevent proper functioning of both the ignition and starter systems.
  3. Corrosion: Corrosion on the terminals of relays is another common problem that affects their performance. When corrosion builds up, it can hinder electrical conductivity and result in intermittent or complete failure of the relay.
  4. Burned Contacts: Continuous arcing between contacts inside the relay can lead to burning and pitting of these contact points over time. This compromises their ability to make a reliable connection, causing starting difficulties or engine stalling.
  5. Faulty Wiring Connections: Loose or faulty connections between wires and terminals of the ignition or starter relays can disrupt power flow, resulting in erratic behavior such as intermittent starting issues.
  6. Excessive Heat: Relays generate heat during operation which needs proper dissipation for optimal performance; however, excessive heat due to poor ventilation or high ambient temperatures could cause premature failure of internal components within a relay.

To diagnose problems with your ignition or starter relays accurately, it’s recommended you consult an experienced mechanic who has access to diagnostic tools specific for automotive electrical systems analysis.

How to Troubleshoot Issues with Ignition Relay and Starter Relay?

When experiencing problems with the ignition relay or starter relay in your vehicle, it’s important to troubleshoot the issues to identify the root cause. Here are some steps you can take to diagnose and resolve problems related to these relays:

  1. Check for Loose Connections: Ensure that all connections associated with the ignition relay and starter relay are secure. Loose or corroded connections can lead to poor electrical contact, causing malfunctioning of these relays.
  2. Inspect Fuse Box: Examine the fuse box for any blown fuses related to the ignition system or starting circuitry. Replace any faulty fuses as necessary.
  3. Test Relays: Use a multimeter or continuity tester to check if both relays are functioning correctly. For the ignition relay: Disconnect it from its socket and measure resistance across relevant terminals using a multimeter set on Ohms (Ω) mode. If there is no continuity, replace the relay. For the starter relay: Remove it from its socket and apply 12V power supply directly between appropriate terminals while listening for an audible click sound indicating proper functionality.
  4. Voltage Testing: With caution, use a voltmeter to ensure that power is reaching both relays when key positions change during starting process: Ignition Relay: Measure voltage across relevant terminals when turning the key from off position (0 volts), through accessory position (approximately 12 volts), and finally in start position (again around 12 volts). Any abnormal readings may indicate a faulty switch or wiring issue. Starter Relay: Check voltage at relevant terminals during different stages of starting process, off position should have no voltage, accessory position around 12 volts, and start position approximately 12 volts again
  5. Replace Faulty Relays: If testing reveals a defective ignition or starter relay, replace it with a new one that matches the specifications of your vehicle’s model and make.
  6. Seek Professional Help: If troubleshooting steps do not resolve the issue or if you lack experience in automotive electrical systems, it is advisable to consult a professional mechanic for further diagnosis and repair.

Watch Video: Ignition Relay vs Starter Relay:

Last Talk: Ignition Relay vs Starter Relay:

When it comes to choosing between an ignition relay and a starter relay, understanding their functions is crucial.

The ignition relay acts as a switch that controls the flow of electrical power to various components in the vehicle’s ignition system, while the starter relay is responsible for supplying power specifically to the starter motor.

While both relays play important roles in starting a vehicle, they serve different purposes.

The ignition relay ensures that power is distributed correctly throughout the ignition system, allowing key components such as spark plugs and fuel injectors to function properly.

On the other hand, without a functioning starter relay, your car’s engine won’t be able to crank over and start.

It’s essential to diagnose any issues with these relays accurately by conducting thorough testing or seeking professional help if needed.


Are Ignition Relay and Starter Relay the Same Thing?

No, ignition relay and starter relay are not the same thing.
While they are both electrical relays that play a role in starting the vehicle, their functions and locations within the vehicle’s electrical system are different.

Can an Ignition Relay Be Used as A Starter Relay?

In most cases, an ignition relay cannot be used as a starter relay.
The two relays are designed and wired differently, and their electrical ratings may not be compatible.
It is recommended to use the specific relay designed for the starter system when replacing or installing a starter relay.

How Can I Identify an Ignition Relay and A Starter Relay in My Vehicle?

The ignition relay is often located in the main fuse box or power distribution center under the hood of the vehicle.
It is typically labeled or identified in the owner’s manual.
The starter relay, on the other hand, is usually located near the engine or attached to the starter motor.

What Are the Common Signs of A Faulty Ignition Relay or Starter Relay?

Common signs of a faulty ignition relay include intermittent starting issues, no-start or hard-start conditions, and engine stalling while driving.
Signs of a faulty starter relay may include a single click or no sound when turning the key to start, repeated rapid clicking sounds, or the vehicle not starting at all.

Can I Replace the Ignition Relay or Starter Relay Myself?

In many cases, replacing a faulty ignition relay or starter relay can be a straightforward process.
However, it is recommended to consult the vehicle’s repair manual or seek assistance from a professional if you are not familiar with the electrical system or lack the necessary tools.

About the author

Latest posts