When this same issue occurred on our previous coach with a 7KW Onan Marquis generator, I found the remote wiring harness had butt connectors about 12 inches along the wires from where they entered a plastic wirewrap at the generator end. One of the connectors had corroded enough to separate from the wire. I replaced all of the butt connectors with soldered and shrink wrapped connections, and had no further problems.
Also, a close look at the A1 board traces will show that the remote connections are simply paralleled with the on board switch connections. If the on board switches work correctly the board is good other than a possible damaged trace or connection, both easily remedied without an expensive board replacement.
