How to Test for Electrical Continuity

This is a V-O-M (Volt - Ohm - Meter) or Multimeter. It will accurately display voltage and resistance (in ohms) when used properly. The one pictured will also display frequency, capacitance and amps. It can provide an audible signal for continuity and test delicate PN junctions like those found in diodes.
Steve C/Wikimedia Commons/CC BY 2.0

Electricians have several different diagnostic tools that they use in the course of their work. These are crucial safety tools that keep electricians out of harm's way and tell them if there is trouble on a circuit or device. Two primary tools include the continuity tester and the multi-tester.

Continuity Tester

A continuity tester is a device that is powered by batteries. It has a pointed metal probe on one end  and  a wire lead with either an alligator clip or a probe at the other end.

It is used to test the continuity of metal pathways, and you can see how it operates by simply touching the metal probe and the wire lead together—by doing this, you complete a circuit pathway, and a light or buzzer will go off to indicate there is a complete, continuous pathway exists. Any electrical pathway can be tested in similar fashion.

These testers are great for checking to see if a device such as a single-pole switch is working properly, or to check lamp wiring to see if the electrical pathway is intact. 

  • Warning! Unlike some other testers, a continuity tester is not designed to be used on live wires. Be sure to turn the power off to the circuit or device that you'll be testing!

Continuity testers are also great for checking wire runs to see if the circuits are complete. In skilled hands, the continuity tester can even determine if a short circuit exists. If, for example, two wires within a sheathed cable have melted together, the continuity tester will light up if you touch one probe to the black wire and the other to the white wire.

Once again, be sure the power is off before doing any testing.

Multi-Tester

As the name implies, a multi-tester is a diagnostic electrical tool that tests for multiple electrical issues. You can test a system for either AC or DC voltage, amperage, open-circuit or short-circuit problems, and you can also test to make sure the circuit pathways are intact and continuous— known as a continuity test.

 

The tool has two wire leads—one red, one black—that plug into sockets on the tool. The opposite end of the leads are fitted with metal probes. On the face of the multi-tester, a dial or digital settings allow you to set the tool to the type of test you wish to conduct.

Testing continuity with a multi-tester is done by using the ohm setting on the tool, which measures resistance of an electrical pathway. In essence, the less resistance in a pathway, the greater the continuity. For example, if you touch the two wire leads on the multi-tester together,  it should read 0, or no resistance (perfect continuity). If the tool shows Infinite resistance, it indicates there is no pathway whatsoever. 

Used this way, the tool can tell you if the connection through a device is complete or if it is opened and is no longer usable.

How to Use a Multi-Tester to Test for Continuity

  1. To test for continuity, turn the dial or set the digital controls on the tester to the ohm setting.
  2. In this mode, you also have the ability to set a multiplier factor, which can be slightly confusing if you are unfamiliar with the tool. Since the testers are designed to test for a wide range of resistance on sophisticated electronic parts, it has "multiplier" ohm settings, indicated by markings such as X1, X10, XK1, etc., controlled by a dial or buttons. These multipliers that tell you that the reading on the ohm meter should be multiplied by the number indicated on the dial. For example, if your dial is set for X10 and the meter reads 50 ohms, the actual resistance number is 10 x 50, or 500 ohms. 
  1. For simple continuity tests of switches and other devices, the multiplier settings are not important. No matter how the tool's multiplier dial is set, you will be looking for a reading of 0 ohms to indicate perfect continuity in the switch or whatever device you are testing. Some meters have an audible alarm that indicates perfect continuity (0 ohms resistance). 
  2. Touch one probe of the tester to one side of the pathway, and touch the other probe to the other side. In the example of a single-pole wall switch, you will be touching the probes to the two screw terminals on the side of the switch. With the switch's toggle lever in the ON position, the multi-tester should read 0 if the metal pathway in the switch is properly intact.