How to Fix a Bad Starter Relay

Symptoms That Your Starter Relay is Going Bad (Culprits, Repairs, and Costs)

Starter relays are small enough to be hard to spot within the vast electrical jungle of your car, yet a bad one is terrible enough to cause electrical gremlins that refuse to let your engine start.

But apart from an engine that doesn’t wake up, there are other common symptoms we’ve grown to familiarize and deal with that mark the end of your starter relay’s life, which is why this guide exists!

And since we’re feeling extra generous, we’re also throwing in some of the associated causes, fixes, and how much you need to unload your wallet to get a bad starter relay replaced right here! (spoiler alert: not that much)

What are the symptoms of a bad starter relay?

Common symptoms of a bad starter relay include having difficulties starting the engine (intermittent starting) or the engine not starting at all.

A bad starter relay can also cause the headlights to dim when starting the engine and the starter motor can remain on even after the engine starts.

Engine Doesn’t Start (With or Without Clicking Sound)

Engine Doesn't Start (With or Without Clicking Sound)

One of the most common and obvious symptoms of a bad starter relay is, of course, the engine not starting up or “turning over” despite turning the ignition key or pushing the start button.

Every time you turn on the ignition, electrical current from the battery needs to pass through the starter relay, starter solenoid, and eventually the starter motor to turn the engine on.

However, if the starter relay goes bad, electrical current will not be able to reach the starter motor, so there will be nothing to actuate the turning over of the engine.

Depending on how bad the starter relay has become, you may still be able to hear a clicking sound as you try to turn on the ignition.

An audible clicking sound means that your starter relay hasn’t gone completely bad yet, though it also means that it’s not transmitting enough electrical current to energize the starter solenoid and activate the starter motor.

It’s also worth checking the fuse for the starter relay in the vehicle’s fuse box, as it can also be blown. 

If you don’t hear any sort of clicking at all, then your starter relay may have gone completely bad already. Nevertheless, whether you hear clicking or not, it’s best to have it diagnosed by a mechanic right away.

Difficulty Starting the Engine (Intermittent Starting)

Sometimes even with a bad starter relay, you can still successfully turn the engine on, albeit only being able to do so intermittently.

If you’re struggling to turn on your car or it takes longer to do so, then you first need to narrow it down by checking things such as your battery and alternator via a voltmeter or multimeter.

Once you’ve confirmed that both your battery and alternator are still working fine, you can start looking into your starter relay, which can either be a small black cube in the fuse box or a separate cylinder mounted on the vehicle’s fender.

In the case of intermittent starting issues, the starter relay may have been exposed to corrosion, dirt, or any sort of debris that builds up on its contact points, which prevents it from allowing electrical current to properly flow through.

The starter relay can also go bad due to being exposed to too much heat, which isn’t good for electrical circuits and components.

Any of the reasons above can cause issues with starting the engine right away due to the reduced flow of electrical current from the starter relay to the starter motor.

Headlights Dim While Starting the Engine

Headlights Dim While Starting the Engine

If your vehicle has a bad starter relay, then one symptom that you may notice is that your headlights get dimmer as you attempt to start the car.

But again, the headlights getting dimmer can also be caused by other things such as a weak battery or an issue with your alternator.

In general, the starting system demands a lot of power from the battery while you’re turning on the ignition, and this is made even more obvious by a bad starter relay as the headlights would go dimmer than usual.

Starting System Remains On After Engine Starts

Another symptom of a bad starter relay is that the starting system stays on even after you’ve successfully turned on the engine.

As its name suggests, the starting system, which includes the starter relay, starter solenoid, and starter motor, is only activated when turning on the engine and should shut off automatically after a successful start.

But if even the starter relay alone stays on, then it can continuously supply a surge of electrical current to the rest of the starting system even after the engine is already running.

Due to the nature of a starting system’s job, it’s designed to only stay on for a short period of time, so a bad starter relay that stays on will wear out and overheat the rest of the components and even the flywheel that the starter motor engages with.

Thus, you should waste no time if you notice that your car’s starting system keeps on cranking the engine even if it no longer needs to, as severe damage can be done to the starting system, electrical system, and flywheel.

What is a starter relay?

A starter relay is a small device that is used to send electrical current to the starter motor when starting an engine.

The starter relay receives electricity from the battery and then passes it to the starter solenoid, which then transmits the current to turn on the starter motor.

What is a starter relay

As part of the starting system, the starter relay bridges the gap between the battery and the rest of the starting system components, which include the starter solenoid and the starter motor.

Depending on the vehicle make and model, the term “starter relay” may even be used interchangeably with “starter solenoid”, making them one and the same.

In most vehicles, however, the starter relay is a completely separate electrical switch that transmits power to the starter solenoid, which is typically attached to the starter motor itself and engages it directly when starting the engine.

Starter relays can vary in form depending on the vehicle and where they’re located. The fender-mounted cylinder-type starter relays (also called 4-post solenoids) are most common in older vehicles, while more modern starter relays are in the fuse box.

How do starter relays work?

A starter relay contains a terminal for the ignition switch, and every time you turn on the ignition, the switch activates the starter relay.

The starter relay then receives and sends electrical current from the battery to the starter solenoid, which activates the starter motor and starts the engine.

Most starter relays are called “make-break” relays that contain four different terminals that either send or receive electrical current.

The two main terminals of the starter relay are the terminal connecting to the positive battery terminal, denoted as “terminal 30”, and the terminal connecting to the starter solenoid, denoted as “terminal 87”.

The two other terminals have smaller wires that provide power to the starter relay, which are the terminal connecting to the ignition switch, denoted as “terminal 86”, and the terminal connecting to the chassis ground, denoted as “terminal 85”.

Starter Relay Wiring Diagram

When turning the key in the ignition or pressing the engine start button, the ignition switch sends power to the starter relay via terminal 86, which then allows electrical current from the battery to go through terminal 30 and into the relay.

Since the starter relay acts as both a circuit breaker and circuit completer that regulates current coming from the battery, having no starter relay in between will result in the starter solenoid and the starter motor not having enough power to activate.

What’s the difference between a starter relay and a starter solenoid?

A starter relay is an electronic switch that aids the starter solenoid in sending the battery’s electrical current to the starter motor.

A starter solenoid is an electromagnetic device that is actuated to activate the starter motor.

difference between a starter relay and a starter solenoid

Starter relays and starter solenoids can be easily confused with one another for two good reasons, the first of which is that both terms are sometimes used to refer to the same thing in some vehicles, as older cars didn’t really use relays back then.

The other reason is that they both have an important role to play in making sure the starter motor receives power to turn on the engine.

However, the main difference is that the starter relay is a small electronic switch that transmits the battery’s current toward the starter motor, while the starter solenoid is a bigger electromagnetic component that activates the starter motor itself.

What causes a starter relay to go bad?

A bad starter relay can be caused by corroded connectors or terminals, dirt or debris buildup, old age, faulty connectors, a faulty starter solenoid, a damaged coil, and exposure to excess heat.

Corroded Connectors/Terminals

Corroded Connectors/Terminals

The starter relay, just like any other electrical component, needs to have its main contact points free of anything that can impede the flow of electricity, and such points include the connectors and the terminals.

If the connectors or the terminals were to get corroded, then the starter relay would not be able to function properly, resulting in the starter solenoid and starter motor not receiving enough current or no current at all to activate.

For this reason, it’s good to check the condition of your starter relay connectors and terminals if they’ve already been corroded. Just be sure to disconnect the battery cables (negative first) beforehand.

While it may be possible to scrape off some of the corrosion from the contact points, you may be better off replacing the starter relay completely in order to get the best possible flow of electrical current.

Dirt or Debris Buildup 

Aside from some rust on the component, the starter relay can also malfunction whenever dirt, dust, or any kind of debris happens to cover the contact points.

With a dirty starter relay, electrical current from the battery would once again not be able to flow normally, since electronic components can be very sensitive to any foreign object that ends up touching their contacts or leads.

The good news is that, depending on how dirty it is, you may be able to clean the starter relay and return it to its original state by using something like a wire brush and some baking powder.

Worn-Out Relay Due to Age

Sometimes, the reason that a starter relay fails is simply because it’s already gone past its useful lifespan, especially if it’s on a relatively old vehicle as well.

Worn-out starter relays will not be able to receive and send electrical current to activate the starter motor.

A starter relay has an average lifespan of about 100,000 miles or 5 to 8 years, so if you’re experiencing issues with starting your car, then it’s also worth checking this small yet crucial component out and replacing it when necessary. 

Faulty Connectors

Faulty Connectors

Sometimes, starting issues may not be caused by the starter relay itself, but rather its connectors that have already become faulty.

If faulty starter relay connectors are the culprit, then you may be able to hear clicking noises when attempting to turn on the ignition yet the engine doesn’t start.

Faulty Starter Solenoid

Faulty Starter Solenoid

In other cases, the starter relay may prove useless if the starter solenoid itself is malfunctioning or damaged, meaning that the flow of electrical current transmitted by the starter relay will be affected.

Depending on the condition of the starter solenoid, the engine may only start erratically or not start at all. This is why it’s also important to inspect the rest of the starter system together with the starter relay.

Damaged Coil Inside Relay

The starter relay contains a coil that’s wrapped around an iron core where current from the battery flows, so if the coil gets damaged in any way, the current will not be passed on properly toward the starter solenoid.

The starter relay depends on the coil to create an electromagnetic field that attracts a switch inside, which in turn creates a closed circuit for the current to flow to the starter solenoid.

Again, depending on the coil’s condition, you may still hear a clicking sound when turning the ignition, but the current will not be enough to energize the starter solenoid.

Exposure to Excess Heat

Starter relays also don’t do well when exposed to too much heat, as this can melt and damage the delicate contacts and other components inside it.

Troubleshooting and Testing a Bad Starter Relay

Troubleshooting and Testing a Bad Starter Relay

To test if a starter relay has gone bad, you can use a multimeter to test the continuity of electrical current between the terminal connected to the battery and the terminal connected to the starter solenoid.

No continuity means that the circuit is open and the starter relay already needs replacing.

1. Park Vehicle in a Safe Space

First off, before you even begin to troubleshoot your car’s starter relay, you need to park in a safe space away from other traffic or anything that can affect the process. This includes the weather and any other outside elements.

2. Wear Safety Gear

You’ll be handling electrical components when troubleshooting and testing a starter relay, so it’s best to wear some safety gear such as gloves and goggles as much as possible.

3. Unplug Battery Cables

After you’re done preparing, you can start by disconnecting the black negative (-) battery cable first then the red positive (+) battery cable after.

Make sure to check for any signs of corrosion or debris that has accumulated on the battery terminals.

4. Clean Terminals on Battery

If there’s corrosion or any debris on the battery terminals, you can clean them by using a combination of an electronic cleaner, a wire brush, and some water to rinse them. Be sure to dry them afterward with a clean cloth or a blower.

Just in case you don’t have an electronic cleaning solution, you can alternatively use baking soda to clean the battery terminals.

5. Locate Starter Relay (Fuse Box/Fender Box)

The next step is to actually locate the starter relay, which can vary depending on the vehicle and the type of starter relay it is.

Starter relays in older vehicle models are usually of the cylindrical type, which are located separately and attached to the fender of the vehicle.

However, other starter relays can also come in the form of a small black cube that is connected to the vehicle’s fuse box, which is either located within the engine bay or underneath the instrument panel of the vehicle’s interior.

Once you’ve located the starter relay, unplug all the wires (for cylindrical type) or remove it from the fuse box (for cube type) and inspect for any corrosion or damage to its terminals. If necessary, clean them just as you did with the battery terminals.

6. Test Starter Relay With Voltmeter

How to Test a Starter Relay (Continuity Test):
1. The relay has four terminals, namely the terminal going to the battery (30), the terminal going to the chassis ground (85), the input terminal going to the ignition switch (86), and the output terminal going to the starter solenoid (87).
2. The negative battery cable should be disconnected first and only the positive battery cable should be plugged in.
3. To test for continuity, first disconnect terminal 30 (going to battery) and terminal 87 (going to starter solenoid).
4. Using a multimeter, attach one of its test probes to terminal 30 and the other one to terminal 87 of the starter relay.
5. If there is continuity between terminals 30 and 87, then it means that the circuit is still closed and the relay is still working. Otherwise, no continuity means the starter relay is not working and needs replacing.

How to Fix a Bad Starter Relay

To fix a bad starter relay, check if the terminals, connectors, and relay box contain any sort of debris, then clean them as needed.

You can use an electronic cleaner, baking powder, a wire brush, a towel, and a blower to clean the starter relay’s components.

How to Fix a Bad Starter Relay

A starter relay can become bad due to corrosion or any kind of debris that has built up on its components, so giving it a proper cleaning may restore the relay back to its usual performance.

Cleaning the Terminals/Connectors

Both the starter relay terminals as well as the wire connectors are exposed to the elements, which means that they are at risk of getting dirty or corroded.

By using an electronic cleaner or some baking powder, you may be able to remove rust or debris from the terminals and connectors so that the starter relay can properly transmit the electrical current again.

Cleaning Inside the Relay Box

On cube-type starter relays that are connected to the fuse box or relay box, you may need to inspect inside the relay box where the starter relay is connected to see if it also has any sort of corrosion or debris.

In that case, you should also clean the fuse box or relay box to prevent the starter relay (as well as any other relays and fuses) from malfunctioning.

How to Replace a Bad Starter Relay

To replace a bad starter relay, first unplug the negative battery cable and locate the relay either in the fuse box or on the fender.

Depending on the vehicle and type of starter relay, you may need a socket wrench, a wire cutter, a screwdriver, or some pliers to remove and replace the relay.

How to Replace a Bad Starter Relay

If a starter relay is already bad beyond repair or “cleaning”, then it’s time to replace it, which is actually pretty straightforward.

Whether it’s the cube type located in the fuse box or the cylindrical type mounted on the fender, the starter relay’s location will be included in your specific vehicle’s owner’s manual.

But before you even get to the starter relay itself, remember to first disconnect the negative battery cable with a socket wrench to prevent any unwarranted electric shocks.

After locating the starter relay, you can then disconnect all of the wires from each terminal. Be sure to take note of which wire connects with which terminal to avoid mixing them up for the new starter relay.

As for starter relays in the fuse box, simply pull them out carefully with some fuse pullers or pliers. Some may be easy enough to be removed just by hand. 

With a new replacement starter relay in hand, install it in the same spot and reverse the entire procedure while ensuring that every screw has been tightened, including the ones for the battery terminals.

How much does it cost to replace a bad starter relay?

Replacement costs for a starter relay can vary depending on the vehicle, though the average is about $50 or more in total.

A new starter relay is relatively inexpensive with some being as cheap as $2 and others costing as much as $30. Labor costs would add an extra $30 on average.

Frequently Asked Questions (FAQs)