W119527 JB51393141 Arrived on site to perform diagnostic on transfer switch due to utility power being present in the area, but generator and ATS are still supporting site. Found a main disconnect to be in the off position. After verifying with multiple national power representatives, I was able to turn main disconnect to the on position and transfer power back to utility position. Generator shut down like normal with no issues to be found. Sot is safe and secure, generator and switch are standing by. I also topped off unit with fuel. Unit was at 74% on arrival, I filled it to 86% and added 60.12 gallons of diesel.