12v power to board is good. I replaced the power board thinking their might be a board issue. New board=same problem! Still a C fault. With 12v wires disconnected the supply power is 12v strong. When the wires are connected to the power board the readings fluctuate from 8-ish to 10-ish volts?? It’s in a class A Winnebago 33V. With the engine running my supply voltage is 14v strong but the C fault again remains. Any ideas or suggestions??