A starter relay is a small but essential part of your car’s electrical system. If it goes bad, your car may not start. This blog post will discuss the symptoms of a bad starter relay, how to test it, and how to replace it. We will also answer some of the most frequently asked questions about starter relays!
One of the most common signs of a bad starter relay is when the engine fails to crank or start. Other symptoms of a bad starter relay include the engine stalling or running rough, the starter relay not coming on, and a clicking noise from the engine area.
What Is A Starter Relay?
Before getting into how to know if your starter relay is bad, let’s find out what a starter relay does and its basic functions within the car system.
A starter relay is an electrical component that controls the starter motor and solenoid circuit in your vehicle. It is a high-current switch that supplies electricity to your car’s starter motor. It is normally controlled by the ignition switch circuit.
When you turn the ignition key, a little quantity of electricity is transmitted from the battery to the starter relay.
This triggers the relay, allowing significantly more electricity to travel from the battery to the starter motor. The motor then turns on the engine, and your vehicle begins to move.
In your starting circuit, a completely working starter relay is a crucial safety element. The car will not start if the starting relay, the starter motor, or any other electrical system component fails.
Symptoms Of A Bad Starter Relay
The main function of a starter relay is to work as a switch for the starter solenoid by switching on a large current stream from a smaller one generated by the ignition switch circuit.
It does the same for the starter motor when it is in a car. Due to the low price tag, replacing the component is the best option when it fails.
But how to tell if the starter relay is bad? Well, these are the warning signs to be aware of.
#1. Vehicle Won’t Start.
Typically, when the starter relay dies, the most obvious symptom is that the car won’t start. Even when using electronic keys, it’s possible that the problem is the starter relay. Even though these keys don’t use a manual ignition switch, the starter relay is still activated when the button is pushed.
Regardless of whether you are turning a key or pressing a button, when the vehicle won’t start, it could be the starter relay. Most often, it’s due to the failed circuit that prevents the ignition system from engaging.
#2. Starter Remains on with the Engine Running.
After you start the car, you either release your key or stop pressing the button. At this time, the circuit is supposed to close, and everything should continue running as normal. This closed circuit removes all power from the starter motor.
However, when the main contacts of the starter relay become welded together, it can stay stuck closed. You will know this happens because the starter stays activated even though the engine is running. You will know this is occurring based on the whining noise you should hear.
If the starter relay remains stuck on, further damage is going to occur to other components. Not only will this problem harm the relay, but it could also damage the circuit, starter, and transmission flywheel.
#3. Intermittent Starting Issues.
When the starter relay works as it should, it sends power to the starter every time you engage it. However, this part can become contaminated by dirt, debris, and excessive heat. These conditions can force the starter relay to work intermittently.
If you start the vehicle and it doesn’t activate right away, but you try it again and it works, it might be the relay going bad. Thankfully, you are getting a warning that the starter relay is going bad, allowing you time to get it fixed before you are stranded.
If the relay itself isn’t going bad, it’s also possible that there’s a faulty wire connection or one that has become corroded under the hood.
#4. Clicking Sounds.
You might hear clicking noises when the car battery is low on amperage, but it could also be a sign that the starter relay is going bad. It happens when the relay can’t send out the full signal.
Most times, the relay operates on an all-or-nothing basis. It’s either going to send a complete electrical current or it won’t send anything. However, when the starter relay becomes damaged, it’s possible that only a partial signal gets sent. This is what leads to a clicking sound when you attempt to turn the key.
Function of Starter Relays
The primary function of the starter relay is to serve as a protective electrical barrier, separating two distinct circuits within the vehicle.
The starter motor is a high-amperage device, typically requiring 60 to 200 Amps in gasoline engines, and significantly more in high-compression diesel applications. This immense current is necessary to overcome the rotational inertia and compression resistance of the engine’s internal components.
If this high-amperage current were routed directly through the ignition switch and the wiring harness, the components would quickly overheat and melt. The relay solves this challenge by establishing a low-current control circuit separate from the heavy-duty power circuit.
When the driver turns the ignition key, they activate a momentary switch that handles a small, safe current, often less than 1 Amp.
This minor current is channeled to the relay, which is positioned close to the battery and starter, allowing for short runs of thick, high-capacity wiring to handle the heavy load.
How does a starter relay work with others?
A starter relay is used to send a signal from the ignition to the starter solenoid, which in turn activates the starter motor. The starter relay typically has four terminals: one for the battery, one for the ground, one for the ignition switch input, and one for the output to the starter solenoid.
When the key is turned to the “start” position, current flows through the coil, activating the electromagnet inside. This attracts a switch arm or plunger, closing a circuit and allowing current to flow to the starter solenoid. The solenoid then activates the starter motor, which turns over the engine.
Similarly, when the key is turned to the “off” position, the current stops flowing to the coil, which deactivates the electromagnet. This releases the switch arm or plunger, opening the circuit and cutting off the current flow to the starter solenoid.
So, you can see that without a properly functioning starter relay, a vehicle will not be able to start. If you suspect that your starter relay may be faulty, it is essential to have it checked by a professional as soon as possible.
Location of Starter Relays
Based on the make and model of your car, you can find the starter relay in several places. It is usually located in the fuse box located under the hood, near the battery.
However, some cars have fuse boxes in the trunk or under the dashboard. If you cannot find the starter relay in either of these places, consult your car’s owner’s manual for its exact location.
Starter Relay Replacement Cost
Starter relay replacement generally costs between $50 and $200, with parts typically costing $10–$70 and labor around $40–$150, depending on vehicle make and model. It is a relatively simple repair, often DIY-friendly, but costs may be higher if a mechanic is needed for diagnosis or to access hard-to-reach relays.
Replacing the starter relay is relatively easy, and you won’t need any special tools for it. If you are inclined or able, you may want to make the job yourself and save a little money by changing it yourself.
Can you jump-start a car with a bad starter relay?
While you can try jump-starting a car with a bad starter relay, simply jump-starting the battery most likely won’t help at all. But if you use the jumper cables to run the starter motor manually, that would help.
How do you check if a starter relay is working?
The easiest way to check if a starter relay is working is to use a multimeter. First, you need a wiring diagram to find which pin will output power to the starter motor. Then measure the voltage on that pin when you turn the ignition switch to the start position.
How do you bypass a starter relay?
You can bypass a starter relay by bridging the power input and power output pins to the relay. But to know this, you need to use a wiring diagram and a multimeter to make sure you’re doing it right.
Are a starter relay and a starter solenoid the same thing?
No. The starter solenoid is located on the starter motor, and a starter relay is in most cases located in the fuse box in the engine compartment. They serve two different purposes.