2007 Jeep Wrangler - Relays

What is a Relay in a Car?

Modern vehicles are equipped with a variety of relays that are designed to automatically control the flow of power in many different engine, lighting, and accessory electrical systems. Relays use a low-current electrical signal from a switch, sensor, or even the engine control module (ECM) on the vehicle to close a circuit and send higher-current power to the appropriate accessory. Some of the most common relays on your vehicle might include a fuel pump relay that turns the fuel pump on when you start the vehicle, an A/C clutch relay that cycles your air conditioning compressor, and the horn relay that allows the horn to honk when you press the switch. Relays are available in a variety of sizes, shapes, and configurations, and may have a design or fitment specific to your vehicle. If you suspect that a relay on your car or truck may have failed, shop O'Reilly Auto Parts for a complete selection of relays to make your repair.

Bad Relay Symptoms

Since so many electrical systems on your vehicle are controlled by relays, it can sometimes be difficult to tell if a bad relay is the source of the problem. Relays can fail completely, or may begin to work only intermittently, when they are damaged or worn out. They can also fail in the closed-circuit position, which may keep power flowing when the vehicle is shut off. If you've noticed your horn continuing to honk or your starter continuing to spin after you've released the horn button or ignition switch, if your fuel pump runs continuously even when the vehicle is not on, or if you hear clicking noises under the dash or in the engine compartment when attempting to turn an electrical accessory on or off, it may point to a bad relay. You can test relays using a multimeter in some cases, but they are often very easy to swap out to determine if the relay has failed.

How to Change a Relay

Most relays are very straightforward to remove and reinstall for testing or replacement. Relays may be located in the fuse box inside the interior of your vehicle or in the engine compartment, and in some cases, banks of relays may be mounted under the dash or on the firewall. If you're looking for a specific relay and aren't sure where to look, you may need to check your owner's manual or service manual to determine its location. Typically, removing a relay can be done by hand, and they can simply be pulled from the fuse box or wiring connector. Once the old relay is out of the way, ensure the new relay is in the correct orientation and press it into place. You can then test the circuit by turning on the non-working accessory, and if it works, then you know that the relay needed to be replaced. If a new or known-good relay is used and the circuit still isn't working, then you can determine if you need to proceed with further diagnosis and repair. O'Reilly Auto Parts carries brake relays, A/C relays, lighting relays, wiper relays, and more to help keep all of the electrical systems on your vehicle operating safely.