For most weekend mechanics, automotive electrical systems can be one of the most intimidating to work on because you can’t see what the electricity is doing or where it’s going. In reality, it’s not difficult.
The people behind Engineering Supplies give their thoughts about this task:
Any electrical component in your car follows the same circuit pattern. First, power comes from the source (batteries) and flows to the load (electrical components, such as your headlights, horn, A/C blower, and fuel pump). Along that route are protective safety devices, such as a fuse and a relay for loads that require a larger supply of electricity.
Take the headlights as an example; it is a simple enough circuit with both a fuse and a relay. There may be moments when the headlights won’t turn on. Assuming all other electrical components work, you will soon figure out that the power source is functioning properly.
In this case, the first thing to check is the fuse and the relay. These protective components wear easily because of the large current and the frequent use of the headlights. If one of them is not working properly, replace it to make the system work again.
When you find no problems with the protective components, the next thing to check is the load itself or the bulbs. If busted, replace them. Check for a loose cable connection or a severed wire. If severed, tap severed ends together and wrap carefully with electrical tape.
Lastly, the switch might be faulty, so it’s important to check that. All these automotive electrical supplies are available from your neighbourhood automotive supply store. The diagnostic method is the same for all electrical components, like windows, the radio, and horns.
Just one friendly reminder: when replacing electrical components, be sure to replace them with the same specification as that of the original equipment. Safety is always a primary concern.