Troubleshoot Car Electrical Problem Copyright AA1Car Troubleshooting electrical problems can be a frustrating task,but it does not have to be if you keep a few simple rules in mind: Every circuit needs a power source;most electrical devices require a minimum voltage to function correctly;and all circuits require continuity. Consequently,most electrical problems are caused by low voltage (or no voltage),excessive resistance or a loss of continuity. SAFETY CONSIDERATIONS Safety is always an important consideration when working on automotive electrical systems. Except for the high voltage side of the ignition system,and the high voltage battery and circuits in hybrid vehicles,there is NO danger of being shocked. Twelve volts (12v DC) is not enough to be felt. The load point is the element that the circuit is supposed to power,such as a light bulb,wiper motor,blower motor,idle stop solenoid or whatever. And,all you need to quick check it is a voltmeter or a 12-volt test light that glows when there is voltage. A voltmeter is the best tool for this purpose because it will give you an exact reading,but a test light is OK for performing quick voltage checks. Using a test light is a quick way to check for voltage,but a voltmeter is more accurate. Suppose you find no voltage at the load point maxitpms. Ah ha,you have discovered your first clue about the problem. Check the fuse,fuse link or circuit breaker that protects the circuit,or the power relay that supplies voltage to the circuit. If the problem is a blown fuse,replacing the fuse may restore power temporarily,but unless the underlying cause for the overload is found and corrected,your"fix"probably will not last. Whatever you do,do not substitute a fuse of greater capacity. A larger fuse may be able to handle a greater load but the wiring and the rest of the circuit cannot. A circuit designed for a 20 amp fuse is designed to handle a maximum of 20 amps. Period. A faulty circuit breaker or an open relay will have the same effect as a blown fuse.Checking the load point for full battery voltage will tell you whether or not sufficient voltage is getting through,and to do that you need a voltmeter. The battery itself should be at least 70 percent charged and read volts or higher ( volts is fully charged). If the battery is low,it should be recharged and tested. The output of the charging system should also be checked,and be about to volts higher than battery base voltage (around 14 to 14-1/2 volts). If the battery is OK,your voltmeter should read within 1 volt of battery voltage at the circuit load point in any given circuit Auto Code Scanner. Low circuit voltage is usually caused by excessive resistance at some point in the wiring. Usually this means a loose or corroded connector,a faulty switch or relay or poor ground. To find the point of high resistance,use your voltmeter to do a"voltage drop test"at various points throughout the circuit. If the voltmeter shows a drop of more than a volts across any connector,switch or ground contact,it means trouble. Ideally,the voltage drop should be no more than volts. If low voltage is detected in a number of circuits,do a voltage drop test across the battery terminals and engine/body ground straps. Loose or corroded battery cables and ground straps are a common cause of voltage-related problems. Clean and tighten the battery cables and/or ground straps,as needed. Sometimes undersized wiring can cause low voltage. Does it only happen when the engine is hot or after the circuit has been on for a period of time? Using a hot air gun or hair dryer to heat wires,connectors,switches and relays can sometimes help identify troublesome components. Environmental factors often play havoc with electrical systems,too. Road splash or water leaking through a crack in the cowl,under the windshield or around a grommet can sometimes short out a circuit. Look for obvious signs of corrosion or leakage,and if you find none check the condition of nearby weather seals. A final note on repairing electrical faults: When splicing wires do not just twist them together and wrap electrical tape around the connection. Use a solderless crimp-on connector,or twist the wires together,solder them and use shrink wrap electrical insulation tubing to seal the repair.
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