What would cause a guitar to make a high pitched feedback like sound. IT sounds like mic feedback and guitar feedback. The "feedback" sound is constant while not playing. It begains immediately after playing stops. I just got a new switch put in thinking that the problem was fixed and it didn't. When I put the switch on full bass sound the feedback goes away. The guitar has two pick ups. The switch has 3 positions. I'm guessing that one is one pick up the other is both and the other is the other one. My other guitar doesn't do this sound ever with the same settings on my amp. I was thinking that I might need a new pick up for my guitar. Anyone know what is causing this?

I think i meant to post this in tech