Starting your vehicle is a routine process, so it can be quite frustrating when the engine has trouble turning over. You'll suddenly find yourself unable to leave home or stranded in some distant parking lot, forcing you to call roadside assistance or appeal to a stranger for jumper cables.

The battery is often the culprit when a vehicle fails to start. However, the problem might stem from the alternator, starter, or even the connections in the vehicle's electrical system. Problems with one component can also cause trouble with others.

The alternator and battery are both integral parts of keeping a vehicle charged up. The battery holds an electrical charge, and the alternator works to recharge the battery as you drive.

Batteries typically have a fairly short lifespan. Michelle Oxley, writing for the agricultural supply company Blain's Farm & Fleet, says automotive batteries tend to last for about four to five years. If you've had the battery for about this length of time and you're having trouble starting the vehicle, the battery could easily be to blame.

Checking the battery will let you see if there are any obvious signs of distress. Corrosion on the battery terminals can make the battery less effective. NOCO, a battery designer and manufacturer, says the terminals can be cleaned with a wire brush and battery cleaner.

You'll also want to take a look at the wires leading to the terminals. If they are loose, damaged, or corroded, they may be the source of the trouble.

Voltmeters are a helpful tool in testing the battery's charge. By attaching the leads to the terminals, you'll quickly get a voltage output. The automotive site CarsDirect says the reading should be around 12.6 volts when the vehicle is switched off and about 14 to 15 volts when the engine is started.

A number of other symptoms point to a problem with the battery. Les Schwab, an Oregon-based automotive company, says these include inconsistent starting, sluggish cranking, or the failure of interior lights to come on when you attempt to start. Sturtevant Auto, Wisconsin-based a used auto parts business, says a bad battery may also result in a clicking noise when you turn the key.

Batteries are more likely to fail in cold weather and when you have made a number of short trips, which won't give the alternator a chance to recharge the battery. If a jump start is enough to get the engine to start, the engine is certainly the source of the problem. However, a jump might only be enough to revive the battery for a brief amount of time.

A failing alternator might also be to blame for a vehicle that won't start, but it can cause other problems as well. Since this component won't be recharging your battery as you go, your vehicle may start to lose power or even stall out during a drive. The radio, headlights, dashboard lights, and other electronics will start to dim or weaken when this occurs. A jump start may be sufficient to get the engine going when the alternator is at fault, but the engine will likely die soon after.

The alternator may also produce a growling or squealing sound. Les Schwab says that if the component is the source of this noise, it will get louder when you put additional strain on the electrical system by turning on the stereo, heater, or other functions.

Observe the lights as you try to start up the vehicle. CarsDirect says that if the interior lights start out bright but start to fade, the alternator is having trouble. The headlights will also come on brightly and then start to dim.

It has sometimes been suggested that disconnecting a battery cable while the vehicle is running will let you pinpoint the source of the trouble, since the engine will stop if the alternator is to blame. However, Oxley says this is risky since it can cause damage to the vehicle's electrical systems.

Alternators can also produce an odor of burning rubber when they are not working properly. This occurs when wires start to grow too hot from the alternator overheating.

If you have a voltmeter, simply testing the battery can let you know if the alternator is failing. When the battery's charge falls within the normal parameters, the problem lies elsewhere and the alternator is often to blame.

Check the alternator itself for any obvious signs of trouble. NOCO says the belt should be properly secured to the component and spinning freely. Wiring from the alternator to the battery should be properly connected and free of damage.

Sometimes both the battery and alternator will make it more difficult to start your vehicle. For example, Les Schwab says a faulty alternator might overcharge a battery, causing it to overheat and shortening its lifespan.

In some cases, both the alternator and battery may be in good shape but the starter won't be working. Oxley says a broken starter often results in a clicking noise when you turn the key, and the dashboard lights will turn on even if the engine won't turn over. Jump starting a vehicle will also fail to get the engine going if the starter is the issue.