The secret of effective Automotive diagnosis and troubleshooting is to have a logical plan

The secret of effective Automotive diagnosis and troubleshooting is to have a logical plan

The secret of effective automotive diagnosis and troubleshooting is to have a logical, well-ordered plan. Following a logical step-by-step procedure (flow chart) will get you to the root cause of a problem quickly and efficiently. Repair manuals will have a diagnostic flow chart that goes in a logical order. It will ask a question, usually yes or no, and depending on the answer will branch off in two or more directions. The last box in the flow chart will have the problem and how to repair it. The example shown is a simple one. A more complicated system will have branches going into specific tests and then have two or more branches from there, depending on test results. You will need some basic automotive diagnostic test equipment to perform your diagnostics. A 12-volt tester (test light) will tell you if a circuit has power or, when hooked up to the negative side of the circuit, it will tell you if a ground circuit is good. A good volt/ohm meter (VOM) will be needed to perform specific voltage and resistance diagnostic tests. A digital meter is an excellent choice because they are easier to read than an analog meter. I have both digital and analog meters in my toolbox because sometimes an analog meter is best for certain jobs. Most VOM's have an ammeter that will test the alternator output and test for current draws. Make sure the one you buy has one. If you have an older car with a point equipped ignition system, you will need a dwell meter to measure and adjust the dwell angle of the points. A timing light will be needed to set and adjust ignition timing. As with any piece of equipment, read the instructions that come with your meter. It will tell you what the various functions are and how to connect the meter to the circuit for accurate test results. Most meters have a fuse in them to protect them from an incorrect connection. Make sure the one you buy has a fuse and get a couple of spares. You will, at some point, hook it up wrong and be very thankful you have the spares. Most of the troubleshooting on today's cars will be electrical in nature. A good wiring diagram is essential to properly troubleshoot and diagnose any electrical circuit. They usually come in two parts; a schematic and a wiring diagram. The schematic shows the different components of a system and how they relate to each other. The wiring diagram shows the actual wire colors and connections. On all vehicles from 1995 and newer are OBDII vehicles and a scan tool will be needed to retrieve fault codes and give you a starting point for your diagnostics and troubleshooting. For testing the mechanical side of the engine, you will need some more specialized equipment. A vacuum gauge with several adapters can be used to test manifold vacuum and test vacuum operated circuits. A timing light will help with checking ignition-timing and it can be a safe way to test for ignition spark. A compression tester will show you the condition of the piston rings, intake and exhaust valves.
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