LED What?

[hellosailor]

"Some of my sockets are actually plastic so there is no ground function in the socket"
No, there still is a ground function. The outer case *must* be connected to the 12v negative lead for the bulb to work. Whether that is connected directly to ground, or indirectly and switched, it still has to go to ground. Unless the polarity was reversed and it goes to hot.

Earth ground, chassis ground, circuit ground, return, whatever you call it. Yes they are different but again "all catch mice".