Where is the main relay located?

The main relay, a critical component in many electrical systems, is typically located in a vehicle's fuse box or engine compartment. It serves as a central switching device that controls the flow of electricity to various electrical components and circuits.

Understanding the Main Relay

The main relay, also known as the power relay or the starter relay, is responsible for providing power to the starter motor, fuel pump, and other essential electrical systems in a vehicle. It acts as a switch, allowing the flow of electricity when the ignition is turned on and cutting off the power when the engine is not running.

The main relay is usually a small, rectangular-shaped component that is easily accessible in the vehicle's fuse box or engine compartment. It is often located near the battery or other electrical components, making it easy to identify and access for maintenance or replacement.

Locating the Main Relay

To find the main relay in your vehicle, you can follow these steps:

• Locate the fuse box, which is typically found in the engine compartment or under the dashboard.


• Examine the fuse box and look for a relay that is labeled "Main Relay" or "Power Relay".


• If the relay is not clearly labeled, you can refer to your vehicle's owner's manual or a repair manual to identify the location of the main relay.


• Once you have located the main relay, you can visually inspect it for any signs of damage or wear, such as discoloration or cracks.

If you are unsure about the location of the main relay or have any concerns about its condition, it is recommended to consult a qualified automotive technician for assistance.

How do I know if my main relay is bad?

Symptoms of a bad main relay include a car that won't start, or starts but then stalls shortly after, often with a lack of fuel pump priming sound. You may also experience intermittent power loss, a check engine light, difficult starting, surging, or a dead battery.
 
This video explains what a main relay is and its function in the engine: 48sBig Dog50001 AutomotiveYouTube · Aug 16, 2019
Common symptoms of a bad main relay

• No-start or intermittent start: The engine may crank but not start, or the car may start and then immediately stall. 
• Engine stalls: The engine may stall while driving or idling. 
• No fuel pump sound: You may not hear the usual whirring sound of the fuel pump when you turn the key to the "on" position. 
• Check engine light: A malfunctioning relay can cause the check engine light to come on. 
• Intermittent power loss: The car may experience a sudden loss of power, especially during acceleration. 
• Surging or rough idling: The engine may surge or run roughly due to an inconsistent fuel supply. 
• Dead battery: In some cases, a stuck relay can drain the battery. 

You can watch this video to learn how to test a main relay: 1mCarsNToysYouTube · Apr 2, 2023
Troubleshooting tips

• Listen for the fuel pump: Turn the key to the "on" position (without starting) and listen for a 1-2 second whirring sound from the rear of the car. The absence of this sound can point to a bad relay. 
• Check for other symptoms: Look for other signs like the check engine light, stalling, or rough idling, which can provide more clues. 
• Consider the possibility of other issues: Many of these symptoms can also be caused by other problems, such as a bad fuel pump, a faulty starter, or other electrical issues. 
• Consult a professional: If you are unsure about the cause of the problem, it is best to consult a professional mechanic for an accurate diagnosis and repair. 

Is the main relay the same as the starter relay?

The running/crank relay and the main ignition relay are distinct components—the ignition relay provides power to essential circuits (ECM, coils, injectors, etc.), while the crank or starter relay specifically manages power to the starter circuit during cranking.

Can a car start without a main relay?

If the relay is the issue you can turn the ignition on and use a jumper wire with the relay removed to crank the vehicle over.

Where is a relay located?

A relay is most commonly located in the fuse box, which can be under the hood, inside the car (often near the steering column or on the firewall), or in the trunk. To find a specific relay, you should consult the vehicle's owner's manual or look for a diagram on the fuse box cover itself, as locations vary by make and model. 
This video shows where the relays are located in a car's fuse box: 58sHelpful DIYYouTube · Aug 16, 2015
Steps to find a specific relay

• Consult your owner's manual: This is the most reliable way to find the exact location of the fuse box(es) and the diagram for the relays. 
• Locate the fuse box: Look under the hood, in the engine bay, under the dashboard, or in the trunk. Some vehicles may have multiple fuse boxes. 
• Examine the fuse box cover: The underside of the cover usually has a diagram that identifies the function of each fuse and relay by its position. 
• Identify the relay: Use the diagram to find the specific relay you need, such as the fuel pump relay, A/C relay, or starter relay. 
• Use online resources: If you're still having trouble, search for your vehicle's make and model online, as forums and repair websites often have diagrams and instructions for locating specific relays.