Outer Limits 4x4 Board

This is a long shot but thought Id give it a go. Ever since I got my truck there has been what I think is a bad earth. Can not find it anywhere. Firstly the fuel gauge drops off. Then my oil pressure, I get a new sender and still doesnt work. When I put my foot on the brake or wind the windows up and down, my taco drops off too. Any idea's?

I'd try a different dash maybe the dash electrics are stuffed. You could also run new earth.leads from battery to body then from body to.chassis to cover most bases

I had a dodgy earth from the trans to the body. In combination with some other suspect but not totally shite earths (resprayed body etc) it cause the accel cable to earth the motor, letting about a bit of a smoke they put in there...! Cracked earth strap somewhere that doesn't appear to be bad on visual inspection? Can you test each strap for 'continuity' - ie. test if they are cracked etc.