Testing electrical resistance is very simple once you know the basics, and it can save you time and money repairing household items.
Electrical resistance is measured in units called Ohms. Let me start by explaining exactly what an Ohm is. By definition an Ohm is: The unit of measurement used to measure resistance to electrical current.
Here is an easy way to explain it: electricity is like water flowing through a pipe, and resistance is anything that slows the flow of the water.
In it's simplest form, an Ohm check is testing the resistance of a circuit or electrical component from point A to B. For example, let me use the testing of a piece of insulated 1 foot wire. Place one meter probe on the point A side of the wire, and the other meter probe on point B. With the multimeter in the Ohms position, the reading should be around 0-1 Ohms.
Basic Resistance Test
Step 1- Set the multimeter to the proper range.
Set the multimeter to the correct Ohms range to fit the specific resistance of the wire/component you are testing.
Step 2- Zero out and test the meter resistance.
Touch both meter leads together while plugged into the meter. You should have 0 to .3 Ohms of resistance. This will let you know the meter's internal resistance. Note: On an analog meter, use the "zero adjust knob" to bring the amount to zero.
Step 3- Disconnect power from the circuit.
Make sure power is disconnected on the circuit that you wish to test using a circuit tester
Step 4- Touch the meter probes to the test points.
Find two open points on the circuit to place the metal tips of the meter probes. In most cases it does not matter which color lead goes on which point in the circuit when performing resistance tests. The exception to that rule is when testing a diode for resistance.
Do not touch the metal portion of the meter lead while taking your reading, as it will completely throw off the amount of resistance measured.
Step 5- Review the test results.
If your meter displays an open, or you get a high amount of resistance, then the wire is most likely broken. A normal reading is approximately .02 Ohms for a short length of wire. Match the test resistance with the correct amount for the component you are testing.
You can apply these simple basic techniques to check the electrical resistance of just about anything. Most household components have some sort of normal designed electrical resistance. Check the service manual, or contact the manufacturer to see how much resistance the component should normally have.