This is interesting. I do have 1/2 dozen small leads tied together at one point. The Tach, AFR, Oil Pressure, Temp, Power Locks, and Radio are for sure grounded in the same spot. AND! now that I think about it the spot is only a foot or so from the Light switch. Well honestly as long as the engine isn't overheating and I know the reading is a little high with the lights on I can live with it for now. I'm not pulling the dash apart for that. Still need to test during the day.