One of the hardest do it yourself auto repair tasks is solving automotive electrical problems on your own. To be successful you will need a wiring diagram in most cases. But even when you have this electrical diagram in your hand it can still be hard to understand and diagnose circuit malfunctions.
When you are tracing electrical circuits using a standard automotive wiring diagram you always want to work from the load or component back to the battery. Find the load device first, for example: light, horn, solenoid or actuator, then find its ground, and then find the battery on the diagram.
Trying to read a schematic from positive battery voltage to negative or ground does not work well. Always work from your load back toward the battery. This rule is important because it gives you a standard and correct direction of diagnosis. If you have proper power and grounds to your load component then you have just solved your problem on the first diagnostic test indicating that the failure is in the device and not in the wiring.
When you are studying troubleshooting manuals and repair diagrams take note that there is usually only one load component per circuit. This simple fact creates a straightforward diagnostic path with better results.
If you are looking at a large repair diagram, and you see more than one load, example starter, light bulb, backup alarm. You will know that each of these items are on separate circuits, and usually run to separate fuses or circuit breakers. In most cases you will find electrical failures isolated to one circuit.
If you find yourself jumping around into multiple circuits for diagnosis, it’s time to take a step back and return to rule number one of electrical problem diagnosis. First sit down and read the repair diagram until you fully understand how the circuit works. This first step may take a little while but will pay big dividends during diagnosis.
Do not be concerned with how long this first step takes it is not a sign of weakness or lack of intelligence. If you take some time to understand the circuit and the flow of the repair diagram you will be able to pick out the malfunction, much quicker. Spend some time now and save a lot of time later.
Just like most things in life the more you use a troubleshooting manual, the easier the repair diagnosis becomes. This is yet another case of practice makes perfect.