I’ve probed multiple locations on the body that should give me good ground readings. Including one of the screws holding the dimmer to the floor. The results are the same regardless of location. Im using a “Power Probe” tool
If you are getting 12v between the body and the NEGITIVE battery terminal you are missing a ground between the block and the body AND you have a path to the positive terminal of the battery thru any number of things, lights, motors etc.
If you are hooking the positive side of your test light to battery positive it will light up when touched to any ground on the car.
This is why I am asking for specifics on where and how you are testing.
As 67dart273 said. A multimeter will diagnose things better than a test probe light.
Always go from battery negative to your voltage source.
