The main relay of an automobile is undoubtedly one of the most important and crucial components of a car.
It controls the computers and the entire fuel supply system of your car.
At the moment you turn your key even before starting the engine, this relay is what becomes operational, and without it, your car’s computer will not be powered, your car’s fuel system will not be turned on, and consequently, your car won’t start.
So it’s safe to say that without the main relay, your car won’t go anywhere. Main relays are designed to last as long as the life of a car, but being an electromagnetic component, it can fail at some point.
Signs of a Bad Main Relay
It can be difficult for an ordinary car owner to diagnose such problems, but there are still a few basic things that owners and drivers can check to rule out common issues. The main relay is usually located under the dashboard, inside the car’s fuse box, but this also depends on the car’s make and model:
1. The Engine Won’t Start
As mentioned above, the main relay controls the fuel system. If the relay is faulty, it will not supply power to the fuel system’s needs, and if the car doesn’t get fuel, the car won’t start. Although there may be countless other, more common factors preventing the engine from starting, it can happen that the main relay turns out to be the problem.
Unfortunately, this is not an easy diagnosis and it could take time to get to the relay. It’s better to consult a mechanic for the job.
2. Check Engine Light is On
Check engine lights can facilitate diagnostics with an OBD/OBD-II scanner depending on the car’s manufacturing year. The code thrown by the car’s computer can sometimes accurately identify the cause of the problem and make the issue simpler, even for owners. If you have a scanner and know how to use it, you can check the code.
3. The Car Dies Immediately After Starting
If the car struggles to stay running and dies shortly after starting, the main relay may be to blame because it powers the fuel system and the car’s computer, which constantly checks and balances the fuel/air consumption and mixture ratio to ensure proper engine operation.
4. The Car Starts Sometimes, Sometimes Not
If your car does this, it could indicate that the relay sometimes works temporarily and other times fails. This will require you to address the issue as soon as possible, as you could get stuck somewhere with no mechanic nearby. So it’s best to consult a mechanic if you notice this symptom.
5. The Car Won’t Start When the Interior Has Become Hot
If you notice this, it’s due to the heat dislodging the solder joints on the relay and breaking the circuit. This is a recurring problem that will need to be fixed immediately because it can further damage the main relay if not checked in time.
There are a few things you can do to superficially diagnose the main relay that don’t require technical knowledge. This will help you determine if your car’s main relay is going bad or completely dead.
What is the Main Relay?
A car needs a mixture of air and fuel to run, but to control the mixture proportions, complex electrical switches and a dedicated computer are needed to constantly check all these things to ensure proper engine operation and smooth driving. However, often underlying electrical issues cause problems instead of the relays and switches not allowing the car to start.
Similarly, if a car refuses to start, it’s unlikely that the main relay is the culprit, but it’s not impossible. To identify the exact problem, professional assistance is required because complex electrical systems can only be checked by certified mechanics with electrical knowledge and experience, as a slight mistake could render one of the main electrical parts of a car useless, so extra precautions are absolutely necessary.
Tests and Solutions
Diagnosing a bad main relay can be difficult because many factors need to be considered when the problem of the car not starting arises. From fuel to air, to the fuel pump and spark plugs, all these things can disrupt the normal operation of a car. If you have basic car knowledge, you can diagnose your car yourself until you find the problem.
Checking for Clicks When Starting the Car
When you turn the key in 3 steps, the main relay clicks 3 times at different key positions. To check if the relay is working at all key steps, place your hand on the relay and turn the key one step. You should hear a click. This will only unlock the ignition.
Turning the key further should turn on the electrical systems. The relay should give another click at this point. Finally, the last step starts the car, to which the relay should also give a click.
If at any point the relay doesn’t click, there might be a problem.
Tap the Relay
Sometimes tapping the relay makes it work temporarily. If touching the main relay causes the car to start, the main relay is going bad and needs to be repaired or replaced. Replacing the relay is not very difficult, but repairing it will require electrical expertise.
If you can’t start after checking all the basic things to verify, it’s likely that the main relay is faulty or there’s an electrical issue that may have fried the main relay.