YOUR CHARGING SYSTEM IN TROUBLE LOW VOLTAGE, ALTERNATOR ISSUES, AND WHAT THEY AFFECT

What does the average person know about diagnosing and repairing starting, charging and ignition systems? Not really much usually it ends with them spending to much, when the actual problem was never really discovered. Basically electrical and ignition problems are often difficult to diagnose (especially intermittent faults), and that a LOT of electrical and ignition parts are replaced unnecessarily in an attempt to repair problems that are hard to diagnose.

Throwing parts at a problem until it goes away is a very expensive way of fixing faults. The "no return" policy of many parts stores means that once you've installed an electrical or ignition part on your car, you own it.

What if the part turns out to be "defective?" In many instances, there's nothing wrong with the part. The parts store will usually exchange it under warranty. But if the second part also fails to fix the fault, it's obvious something else is at fault. So don't be too quick to blame "defective" parts when a newly installed part doesn't seem to work any better than the old one, or when you get a comeback. Do your diagnostic homework, then isolate the fault and identify any parts that may need to be replaced.

Every so often you notice it: The transmission shifts a little late, or maybe it seems to miss a gear entirely. Then it’s okay again… for a little while. Worst of all, there’s no rhyme or reason behind the condition. One minute it’s fine, the next it’s not.

So you pop the hood to check the transmission fluid level. Then you notice it: A big mountain of corrosion on the battery terminals. You’ll have to take care of that, but it can’t have anything to do with the transmission, right?

Wrong. In fact, there’s a good chance you just found your transmission problem. That’s because nearly every shift on today’s transmissions is operated electrically through a computer system. And that computer system gets its power from — you guessed it! — the battery.

Fuel injection problems encompass everything from hard starting, stalling and misfiring to hesitation, surging and no-starts. Dirty injectors, for example, will restrict the amount of fuel that is sprayed into the engine with every pulse of the injector resulting in a leaner-than-normal fuel mixture. This, in turn, can cause lean misfire, hesitation, poor performance and an increase in hydrocarbon (HC) emissions.

Because EFI is part of the powertrain control module's feedback control loop, problems with the coolant sensor or oxygen sensor also can affect fuel delivery. A coolant sensor that always reads cold will prevent the engine from going into closed loop resulting in a rich fuel mixture and poor fuel economy. A dead oxygen sensor can have the same effect. So too, can a contaminated or sluggish O2 sensor.

The PCM also relies on inputs from the throttle position sensor, airflow sensor (if one is used), manifold absolute pressure (MAP) sensor and intake air temperature sensors to adjust the fuel mixture. Most sequential injection systems use the signal from the camshaft or crankshaft position sensor to trigger and sync the injector pulses. Problems in any of these sensor circuits also can affect fuel delivery.

Most PCMs have an internal driver circuit for grounding (or in some cases energizing) the injectors. Problems here can disable one or more injectors depending on how the system is wired. In some cases, a shorted injector will kill the driver circuit in the PCM. And don't forget the power relay that supplies voltage to the injectors. If this relay dies, it will disable all of the injectors.

There's also the components in the fuel system itself: the fuel pump, pump relay, fuel filter, fuel lines, pressure regulator and injectors. Problems with any of these components may prevent fuel from reaching the engine or reaching it at the correct pressure

EASIEST CHECKS

Blown fuse(s).If one particular accessory, set of lights, or convenience in your vehicle stops functioning altogether, a fuse has probably been triggered. Fuses are simple to diagnose, find, and replace yourself. Just look in your owner’s manual for the location of the fuse panel (your car might have more than one), and the location of the particular fuse for the failed accessory. Using a fuse puller (it looks like small plastic tweezers), slowly and evenly pull the fuse out of the board and hold it up to the light. If the strand of metal that passes through the middle is broken, then the fuse needs to be replaced. Make sure you replace the fuse with one of an identical amp rating (usually color-coded and listed on the outside with an amp rating). If the fuse blows again, then you know there is another problem. Fuses are inexpensive. Auto parts shops sell ‘variety packs’ of various popular fuse sizes—a good idea to keep in your emergency roadside kit. Dead battery, or bad battery terminals. Auto batteries can fail without warning, if they’ve been in service for two years or more or if they’re defective. If you have no juice, make sure your battery terminals are tightened and clean of corrosion. If they’re not, then that might be the cause. If they are snug and clean, use your voltmeter to check the battery by touching the meter’s probes to the battery’s plus and minus posts, scratching slightly to ensure a good connection. With theengine and ignition off, if the voltmeter reads between 10 and 12 volts, then the battery is good (9-9.5 is barely acceptable). Now that you know the battery is good, go back and measure the voltage at the terminal clamps, and then again with the positive probe touching the positive terminal clamp and the negative probe touching the bare metal or frame member that the ground wire (narrower black wire) leads to. If all of these tests measure near the same voltage, then you can rule out the terminals, too. Alternator. A newer battery that won’t keep a charge, the dimming of headlights, or stalling at stoplights are all signs of an alternator that is about to fail completely. If you suspect that your charging system is giving out, test it for certain by touching the probes of your voltmeter to the plus and minus terminal clamps when the engine is running. If it registers between 12.8 and 14.7 volts, this is usually considered within the normal range and your charging system is fine. If the voltage is too low, try the voltage at the alternator output terminals, and if it measures as low, then your alternator likely needs replacement. Fusible link. A fusible link is a higher-capacity connector that protects accessories wired directly from the battery, including the starter. Fusible links can either fail gradually or suddenly, depending on the cause. Sluggish electrical accessories, an unusual pause before the starter turns, and odd behavior of accessories plugged into the power socket are all symptoms of a failing fusible link. If the electrical system is completely dead, the battery cables are tight, and jump-starting does absolutely nothing, then the fusible link has likely failed or been triggered. For replacement, get a proper repair manual for your car or take it to your mechanic. Fusible links can be significantly more expensive than fuses, so check all major electrical connections to see if there’s an obvious problem before installing another one. People sometimes cause fusible links to fail by jump-starting a car with the clamps reversed. Faulty switch. Test the switch that has failed in all possible positions, to see if the accessory works at all, or to test for loose connections or shorts. Particular switches, such as those for headlights, sometimes have built-in circuit breakers. Consult with your owner’s manual or shop manual on how to reset the breaker.