Welcome. My name is XXXXX XXXXX would be glad to assist.
I have read the post and the information you provided.
It sounds like there is not a ground wire in your switch box for
testing as we previously discussed or it may not be connected
to the switch.
So, if you are reading the switch screws only, then that will also show
whether the switch is bad or good.
With the power on, turn off the switch
Place one lead on one screw and one lead on the other screw
What is the reading? It should read 120, then that is good so far.
Now, turn the switch on, and perform the same test.
It should now now read 0
If it reads 0, then the switch is good.
If it reads 120 again as in the first test
REPLACE the switch as it is bad.CLICK HERE for the picture of testing
They are available at any building supply, such as Home Depot, Lowes, or any
local hardware store.
Get a standard Single Pole switch.CLICK HERE and see one at Home Depot,
which you can print
out and take with you.
When replacing the switch, turn off power and remove the switch
from the wall.
There are only 2 wires to disconnect and put on the new switch.
If the wires plug into the back, you will have to cut them and then
re strip the insulation
to expose new copper anfd then use the side screws
on the switch to wrap the wires around and tighten.
The push in on the backs of the switches will tend to fail over time and
the screws will give better performance and longevity.
While the switch is out and power off, if there is a bare ground wire
in the box, you can at this point connect it to the GREEN screw on the switch if you wish and have the switch grounded.CLICK HERE for a video on switch change out.
Hope that gives you the needed information, just reply if you need more.
Sorry I was not on last night after 10pm and unable to respond.