Continuity testers are available at most hardware stores.
They are inexpensive and provide a safe means of testing switch to determine if
it is in working order. With the switch removed from the wires, use the
continuity tester to see if there is continuity through the switch. Do this by
touching the probes of the tester to the terminals with the switch in the ON
position. Power should flow between the top and bottom terminal. If the tester
doesn't light up, the switch is defective. Don't throw it away though; take it
to the hardware store to make sure you get the correct type of switch as a
replacement because, as you will see below, the variety of types of switches
can be confusing.
Types of switches:
There are three types of household switches. A switch that
has only two terminals is called a single-pole switch. It alone controls the
circuit. Then there is a three-way switch. This one has three terminals and one
is marked COM, or common. This is the terminal that the "hot" wire
attaches to and the other two terminals are switch leads. The three-way switch
is used to control a circuit from two different locations, like the top and
bottom of a stairwell for example. A double-pole switch has four terminals and
is normally used to control higher voltage appliances. This type of switch can
be identified by the ON/Off markings on it. A four-way switch also has four
terminals, but no ON/OFF markings. The four-way switch is used along with two
three-way switches to control one outlet, or fixture, from three separate
locations. Most switches, no matter what type, will also have a green terminal,
and this is for the green ground wire.