Learn the basics of electrical troubleshooting and how-to

How to perform basic resistance tests See series circuit See parallel circuit

Checking 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. Lets 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, lets use the testing of a single insulated short 1 foot wire. If you were to put one meter lead on point A side of the wire, and the other meter lead on point B, you should get around 0-1 Ohms, very little electrical resistance. So let us begin.

Turn your meter to the lowest range on the Ohms (Ω) setting.

Touch both meter leads together while plugged into the meter. You should have 0 to .3 Ohms of resistance. Note: On an analog meter, use the "zero adjust knob" to bring the amount to zero.

Using your best guess, or researched information, set the Ohms range on the meter to fit the specific value you want to read.

Make sure power is disconnected on the circuit that you wish to test, if the circuit is powered up, your meter will be severely damaged beyond use.

Lastly, find two open points on the circuit to place the metal tips of the meter leads. In most cases it does not matter which color lead goes on which point in the circuit when performing Ohm checks. The exception is when testing a diode.

Note: Do not touch the metal portion of the meter lead while taking your reading, it will completely throw off the amount of resistance read.

Ohm a wire

If your meter doesn't move, or you get high amount of resistance, then your wire is most likely broken. Now let's say you add into the circuit a light bulb. Now you are reading through the wire and the filament of the bulb, which will give you a reading of resistance of the light bulb plus the wire. So if the resistance of the wire is 1 Ohms, and the bulb filament is 18 Ohms, you have a total of 19 Ohms of resistance in the circuit.

Ohm a wire and bulb

You can apply these simple basic techniques to check the electrical resistance of just about anything. Most household components you will be checking have some sort of normal designed electrical resistance. Check the service manual or with the manufacturer to see how many Ohms it is supposed to be.

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