How long do alternators last?

Alternator Maintenance
A voltmeter is just one way to determine if your car's alternator is in proper working order.
A voltmeter is just one way to determine if your car's alternator is in proper working order.
© Tiraboschi

No one looks forward to being stranded on the side of the road, whether it's thanks to the alternator or anything else that breaks on our cars. Luckily, there are preventative measures we can take to make sure the electrical system won't fail us when we need it most.

There are several ways to test the health of your car's alternator. One way is to use a voltmeter, a device used to measure electrical output. A voltmeter can be found at almost any auto parts or electronics store. Start the car, make sure all accessories are turned off and get the engine at a healthy idle. Select the DC scale on the voltmeter, connect it to the battery terminals and look at the reading on the device.

The voltage should read around 14 volts. Next, start adding electrical devices like headlights, heater and radio -- if at any time the voltage drops lower than 12 volts, then your alternator isn't doing what it should be. Check to make sure it's the same voltage at the alternator terminal. If it isn't, your car's battery may be the problem, not the alternator [source: Hewitt].

If you think the problem is the battery and not another car part, there are a few things you can try before running out and buying a new one. Make sure you disconnect the battery from the vehicle, negative terminal first and then positive. You don't want to unintentionally zap yourself! Try cleaning the battery connections with baking soda and water -- if the terminals are dirty, electricity won't flow properly.

You can also replace the terminal clamps, which can erode to the point where they don't provide contact anymore. There may be soldering involved with the replacement clamps, however, so this job requires a few more tools and a little more time than you may be willing to put in [source: Allen].

If these efforts don't work and the battery isn't the issue, it may be time to replace the alternator altogether. In the next section, we'll discuss the auto part information necessary for the job, and how doing it yourself is easier than you might think.