One of the most common tests when it comes to automotive diagnostics is checking short to ground. Thankfully, your job can be made a lot easier with a digital multimeter. There are several multimeters that are specifically designed for automotive diagnostics, but any multimeter that can measure resistance in Ohms (usually displayed as Ω on your multimeter dial) can do this simple job. If you’re looking for a digital multimeter, have a look at our several comparison posts.
Although it’s not hard to check short to ground with a multimeter (For this task we recommend use Fluke 3340 multimeter), it takes a bit of knowledge to get it right.
In this blog post, we’ll briefly discuss the theory behind checking a short to ground and then provide a detailed overview of the exact steps you need to take to check short to ground with your digital multimeter. Once you know how to check short to ground with a multimeter, you’ll be able to find this common problem and have your first steps to fixing small electrical problems in your appliances or cars.
Ohms and resistance
To check short to ground with a multimeter, you need to measure resistance. Electrical resistance is literally the difficulty that electricity has to get through a component, called a conductor. The more resistance, the harder it is for a current to pass through the conductor. To measure resistance, you have to find the voltage of an object and divide it by the current. Voltage is the capacity of the object, whereas current is an indication of how much of that capacity is used.
The more loss of current compared to the capacity, the more resistance is measured. The proportion between volts and current is measured in Ohms, which is why you’ll need a multimeter that measures Ohms to check short to ground. Luckily, a digital multimeter will automatically do all this math for you, but it’s always helpful to understand the dynamics behind a measurement to know what’s going on.
You can also watch this video for a better understanding of resistance and Ohm’s law:
What is short to ground
Short to the ground is a particular type of electrical problem (that is most common in automotive problems). In short, when you’ve got a short to ground, it means that a live wire is touching something it shouldn’t and is accidentally grounded. In an electrical appliance in your house, this will trip the breaker, and you won’t be able to reset it until the problem is fixed.
In practical terms, it means that there is a leak in your electrical circuit somewhere. If your electrical circuit would be a simple plumbing pipe with water flowing through it, a short to ground is comparable to a big hole somewhere in the pipe that leaks out all the water before it ever gets to its destination.
How to check short to ground with a multimeter
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To check a short to ground with a multimeter, you’ll need to set the dial of your multimeter to Ohms, or another setting that allows you to measure resistance. If you have any of the digital multimeters designed for automotive diagnostics, such as the Innova 3340 (your digital multimeter), simply adjust the dial, but most other multimeters will also have a Ω setting. All the digital multimeters we discuss on our website have the option to measure resistance.
Now that your dial is in the resistance setting, connect one lead to one end of the circuit or component you’re testing. Connect the other end to a good ground. In cars, an uncovered piece of metal will work. Now read the display of your digital multimeter. If the display shows anything other than infinite resistance OL, you’ve got a short to ground. This is because the good ground from one of your leads should create the infinite resistance.
Now that you know how to check short to ground with a multimeter, it’s time to put your knowledge to the test. Remember that if there isn’t a short to ground problem with the component or circuit you’re testing, you will measure something other than infinite resistance. Take some components in your car and make sure you get some sort of reading, and you’ll know the difference when a problem comes up.