,,, when they do not work, is it the switch thats corrupt?

 

there are too many variables to just answer the question as you have asked it.

Is the stereo factory? If not, they were probably not hooked up.

It could be the amp. You would have to check with a tester to find out. See if you are getting input to the amp...and if you are getting output.

By switch, are you talking about the control switch in the center console? What series car do you have?

 

install some tweeters that handle 50 watt rms .easy to find on ebay .what a difference.sweet sound