Diagnosing practically any problem with your car can be a daunting task. Here you'll have something in common with a veterinarian - because both patients can't speak. But like a doctor you need to know the symptoms and run tests to eliminate possible causes. Let's face it though, MD's do have it easy - the human body has the same parts and doesn't change from year to year!

Most people approach diagnosis by throwing parts at the vehicle to see which one "fixes" the problem. This is great if you get it right the first time, but if you're wrong, then you end up wasting a lot of time and money. Getting it right the first time comes down to a science - a science experiment rather - which is the attitude you need to have when troubleshooting difficult problems.

1. The first step should be to define the problem. Ask yourself what is the car NOT doing? For example the car won't start or won't shift. You can also ask what is it doing that it shouldn't? Such as bouncing up and down every time you hit the brakes or smoking like a freight train out of a dead stop. This will help you narrow the problem down to the components involved and not get you sidetracked.

2. Understand the system. This means learning how your car truly works. This is sometimes the only way to correctly tell whether a component is working or not. Now you don't have to know the equation for airflow through the bend radius of the intake manifold but you should know that this is where the engine gets its air. Spending just a few minutes to read the repair manual and learn the system can save you hours of guesswork. For example did you know that most Ford vehicles have an inertia switch that shuts off the fuel pump in case of a crash? How many cars do you think have been towed to shops only to have the mechanic come out and push the reset button? I personally know of 2. The truth is if you don't knowthen you don't know! Automakers do some weird stuff under the hood, so you really will benefit by learning the system before you go out and start tearing parts of the car.

3. Use the process of elimination. This is where you perform tests to eliminate the good parts of the system and get to the root cause. In some cases testing will require replacing with a known good part because we all don't have access to an X-ray machine or semi conductor test facility. Either way the purpose is to separate what does work with what doesn't. Some parts are dependent on others to work correctly a simple example is the alternator. If the battery is bad than it will affect the alternator by increasing the load so as to reduce the voltage. This means you'll get 13 volts when you should get 14. The alternator is doing its job but it's charging a bad battery.

4. The last tip is to keep it simple. Don't look for a shorted wiring harness if your head light is out. Go for the obvious things first and eliminate them before you go any further. Transmission shifting funny? Check the fluid. Brakes feel soft check the pads. The normal wear items on cars are just what they are normal wear items. Don't fall prey to chasing phantom problems when it's right in front of your face.

Using these methods will help you achieve a high success rate of diagnosing any machine problem whether it is electrical or mechanical. You and your patient will be a much happier pair!

Learn more about this author, Louis Winthorpe III.
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