There’s nothing worse than planning a well-needed trip down to the Sunshine Coast only to have it dawn on you that your alternator is faulty. There are many symptoms to suggest that your alternator is bad. Some of these include issues when starting up your vehicle, dull interior lights, unusual noise output from the stereo system, or faint or overly bright headlights. If your vehicle is displaying one or more of these issues, don’t fret. Here is a quick and easy guide on how to test if your alternator is bad, which will be sure to have you coming down to the Sunshine Coast in no time. Before we start, you will need either a voltmeter or multimeter to connect to your car battery. These can be purchased at any automobile store or online at a relatively cheap price.


Step 1: Check your battery

In order to effectively check your alternator, your battery must be charged and in good condition beforehand. To check this, make sure your vehicle is turned off and attach the voltmeter’s leads to the corresponding terminals on your car battery. The red lead of the voltmeter should be connected to the positive outlet of the battery, and the black lead should be connected to the negative one. If your battery is estimated to be below 12.2 volts on the voltmeter, your battery charge is too low to administer this alternator test. If this is the case, charge your battery before proceeding to the next step. Typically, a fully functioning battery will fall between 12.6 and 13.2 volts.

Step 2: Start the car engine

Providing your battery is charged, start your car and rev the engine to 2,000 RPM or above. You do not need to read the voltmeter in this initial test. This is to ensure that your battery power is sufficient and rule out the battery as the source of the problem. It will also force the alternator into a higher gear and, if it fails to do so, that is the first sign that your alternator is damaged or broken.

Step 3: Retest the battery with the voltmeter

Now that your battery is completely tested, it is time to retest the battery using a voltmeter or multimeter. When you read the voltmeter or multimeter with the engine turned on, it should fluctuate between 13 and 14.5 volts. If this is the case, then your alternator is in working condition and adequately fuelling your battery into a higher gear. However, if the voltage does not change with this fluctuation in RPM, then your alternator is faulty and needs to be replaced. You can further your test by putting on your car radio or headlights. Once again, if the battery voltage remains below 13 with this change in power, then your alternator is bad.

If you have a bad alternator, don’t fret. We at Auto Electrics QLD are here to help. Call our team today at (07) 5442 2278 or send an email to