Set me straight!

My knowledge of multimeters is very limited, I've watched videos on how to use one but still don't fully get it. I have a problem with my backup light switch in my 69 Dart 340 4 speed that I think could be bad. I have no reverse or under dash lights. I connected the meter to the switch and set it to continuity (sound) and shift into and out of reverse and I get an intermittent sound while I'm in reverse without moving the shift lever which leads me to think that the switch could be bad. I got a new switch from Advance and tried the same test and I get no sound at all from it by pushing on the ball on the back of the switch with the meter attached to it. I tried 3 different meters with the same result. Where am I going wrong? Thanks for your knowledge.