Charging System Checks Made Easy

Voltage tester
The Innova in-car voltage meter is convenient and accurate. photo by Matt Wright, 2014

Your car or truck runs on fuel, right? That’s what you thought. And you were partially correct. But before fuel, your car needs electricity. It needs juice to turn the starter and a strong spark to fire the engine. Finally, it needs some air to make turn the fuel and spark into fire. In fact, most automotive troubleshooting revolves around establishing which one of those three items is not making it into the combustion chamber.

If your car has been having a no-start problem, you’ve no doubt done some testing on the electrical and charging systems. <P>

Some of the most important tests when troubleshooting automotive electrical systems are voltage tests. You want to know the voltage of your battery before you turn the key, and you need to know the voltage that is being sent back to the battery from the alternator while the car’s engine is running. Once you have these two numbers you’ve gone a long way toward determining what may be wrong with your vehicle’s electrical system. <P>

In the past, these electrical tests have involved a hood-up, pulling over to a safe place off the road, in-depth analyses with often expensive meters and rigs. Back in the ‘80s we had a digital multimeter to read static voltage or battery voltage and a gigantic alternator tester that measured alternator output using a fat, hot heat sink. It was major, not because it was tough to use but because it was a large tool that could not be used on the fly.

On top of that, these tools were really expensive considering how little they measured. <P>

But times really do change. Thanks to technology we have many advantages over the old ways. In terms of charging system checks and diagnosis, there is a tiny, inexpensive tool that can send you immediately in the right direction.

For this write-up, I chose the Equus Innova 3721 Battery and Charging System Monitor, not because it’s the best or the go-to tool. I chose it because it was the cheapest tester they had on the shelf at Wal-Mart so I could prove once again that you don’t need to spend a lot of money to get really good information that will lead you to a correct diagnosis of your car’s engine problems. This handy little meter plugs into your cigarette lighter and actively measures voltage output. With your key in the on position, it will measure the condition of your battery. You’ll want to see something in the neighborhood of 12 volts. Thankfully it’s displayed clearly on the tester’s screen. With the vehicle running you have now switched to measuring the vehicle’s alternator output, usually around 14 volts. To make things even more simple, there colored LEDs — green, yellow and red — indicate the general health of the charging system. This is a major piece of convenience that plugs right into your power outlet (formerly known as the cigarette lighter).  <P>

Now that you know where your system’s weaknesses lie, you can start to improve things. Maybe you just need to clean your battery terminals or replace the battery.

Or maybe your alternator is toast. Either way, you can now measure things quickly — and cheaply! I am so impressed with the ease of use and accuracy of this and similar products that I recommend it to car owners and mechanics alike.  It may not be a direct substitute for the $500 battery and alternator tester, but at a fraction of the cost it's great.