The header tank should always be full of fuel I would think under normal situations. I would have the sensor as high as possible on the header tank. And as I understand this sensor to work, is it will send current down the one wire if the sensor is reading fuel. That in my thinking would go to the green light, which will maybe also tell me everything is working with the sensor. If header tank starts to run empty, the sensor should then send a current down a different wire to the red warning light. Maybe I've got it all wrong, but that is what my plan was based on how I thought it could work. Am I wrong? JImChuk