A car that won't start can be one of the most frustrating problems an owner can have. When this problem occurs, the first thought for many people is to immediately check their battery and perhaps their alternator as well. In reality, there are many parts involved in the ignition of an engine. One part of the car drivers may not know about is called the starter relay, also sometimes referred to as a starter solenoid. Although not as high-profile, this part could be the source of ignition issues in a car.
It helps to understand what the starter relay's role is in getting the engine moving. Drivers aren't wrong if they initially suspect their car's battery may be to blame for their car not starting - after all, the battery needs to have juice in order for the engine to start.
Yet even the most amateur mechanics are probably aware that most vehicles run on combustion engines, not electric motors. So how does a battery ultimately get a mechanical device to begin working? The answer lies in the starter solenoid.
The term "relay" is a good way to remember what this critical car component does. Essentially, it "relays" a large amount of electric current from the battery to the starter motor itself. The starter motor is what eventually gets those pistons moving and allows the engine to start up. When the key is turned in the ignition, it sends a small electrical signal to the starter solenoid. This closes a pair of heavy contacts across the solenoid, which essentially serves as a bridge for the large amount of electric power to get from the battery to the starter.
Thus, the relay is absolutely critical to a vehicle starting properly. Unfortunately, it's not uncommon for starter relays to fail. Sometimes the part will completely fail, in which case the owner will hear nothing when they turn the key in the ignition. Other times, they may notice a clicking sound - this either indicates a low amount of power coming from the battery or a problem with the starter relay's contacts.
The starter solenoid can be found by looking at an owner's manual, but it's generally in the same place on all cars. Drivers can find the starter relay by following the red "positive" wire from their battery. Keep in mind this wire could be the source of the problem too when it comes to the car not starting.
If you want to replace the starter relay, doing so is quite easy. First, ensure the car is off and your hands are completely dry. Disconnect the wires from the battery before proceeding, especially the red one that leads to the starter solenoid. If you do not do this, you could accidentally provide enough an electric spark to the solenoid's contacts to turn over the engine - not something you want to happen as your hands are inside the car.
In some cases, you may notice corrosion on the outside of the starter relay. Safely remove the relay by disconnecting all wires, then use some sandpaper to get all of this gunk off the outside of the relay before replacing it. If this doesn't work, you'll probably have to replace the starter relay outright. This is as simple as buying the correct replacement and installing it right where the old one used to be.
Reconnect all wires, then turn the key. If the starter relay was what was causing the problem, hopefully your engine will roar to life.