Every electrical device dc or ac is a controlled short, light bulbs electronics ect. You have a uncontrolled loop to ground, take you a meter and check continuity from negative post to your frame. It should read near zero or zero depending on how it's calibrated, make sure no paint or debrea is in the way. Sounds like you don't have a good case ground the way it affects everything, find a coming ground point from wiring harness and check landing. If that is not landed well or broke everything will travel through the device with the lowest resistance.