Working on the electrical system of a car is something no mechanic likes to do. Like the veins and arteries of the human body, a car's electrical system is a complex network of connections that are needed for it to function properly. The first issue you will encounter when working on a car's electrical system is how to separate any of the five basic types of car electrical connectors without damaging the wires or losing your mind.
Pull the electrical connection toward you. Make sure that you can comfortably get both hands on the connection. If you cannot, look further along the harness, there may be a plastic tie holding the wiring up behind the dash that needs to be loosened or removed before you can separate the electrical connections.
Hold each side of the electrical connection between the thumb and forefinger of each hand. If your connection is a wide boxlike type continue reading, if not go on to step 3. Box type connections are commonly used for rear signal lights and headlamps. Feel along the wider face of the box near where the two pieces connect. You will feel a tab on one side. Push down on that tab while pulling on the piece that is inserted into the part with the tab. The connection will separate.
Pinch the sides of the rectangular connection that inserts into the other part. If this is not the type of connection you are working on, go to step 4. You will feel a raised tab on the narrow sides of the connection, press these in and pull the inserted part of the connection out of the receiving piece.
Hold the upper portion of a cylinder type connection in the palm of one hand. Cylinder type connections are popularly used for antennas, radios and other accessories in your wiring harness. A cylinder will separate in one of two ways. The first will have a set of tabs moulded into the bottom part that lock into the top piece through notches moulded in the top part. To separate these, press the bottom part into the top and twist counter-clockwise. The tabs will move to the wider portion of the notch and you can withdraw the lower half from the upper. The second type of cylinder connection is a simple threaded type. Hold the upper part in the palm of one hand and grasp the lower half and turn it counter clockwise until it comes free.
Separate simple terminal connections (a male and female metal ended connection that are joined together) by grabbing both halves by the portion of the connection located behind the terminal head and pulling them apart. You can usually tell the part to grab because it is covered with a colour coded piece of plastic or rubber. Do not pull by the wire as you can ruin the integrity of the connection and cause a short.
To help keep track of what connectors go with what, buy a book of electrical labels. This is available in most auto or electric supply stores and is a simple series of pre-printed numeric labels. Before you separate a connection, but a label on each side of the connection that has the same number (one and one, two and two and so on). This will take the guess work out of trying to connect everything when you are done. There is even a log in the label book where you can write down what the connections are for (headlamps, radio and so on). This way you won't have to figure it all out again should you have to work on the electrical harness of the car.
Make sure that all of your connections are firmly in place with no exposed wires or crossed connections. A crossed connection, where a portion of one connection touches another (without insulation in between) can easily cause a car fire.