I often hear electrical faults are traced to defective relays. A relay problem once caused the fuel pump in my car to malfunction and I could not start it. It cost $200 to fix it. What exactly is a relay and how does it function?
A relay is a switch. When an electro-magnet inside a relay is energised, it closes to allow current to flow to a component.
Relays are usually plugged-in devices. Hence they are easy to replace.
Also, as far as automotive components go, they are relatively cheap, usually costing no more than $100.
But once a relay develops a fault, it is extremely hard to repair because of its intricate parts, so it is best to replace it.