Yes, 12 volt is required for the control panel of the water heater. If you have a Suburban heater , remove the black cover with the resets on it & inspect the wires, mine were being crimped by the cover & shorted out.
Figured it out. The fuse on the hot water heater circuit board keeps on blowing. When I watch it when my wife turns on the heater, the fuse blows immediately and a puff of smoke comes off the circuit board. So, it must be the circuit board.
Mark & Susan
'13 Cruiser Patriot 335SS - '13 Ford F150 SCREW - PullRite Superslide - Roadmaster Active Suspension Member - "Northeast Adventures RV Rally Group" & "Mason-Dixon Bunch"