Try Winnebago Industries
and check out the "resources" tab then manuals, etc, etc to find the electrical drawing for your unit. It should help you locate the switch or at least get you close.
Also, look at your AC distribution panel and verify there is a WH breaker. It should be on it's own dedicated breaker. If no breaker then maybe no electric WH.
In our coach it is inside a cabinet over the dining table........seems like an odd place but that's where it is. It looks like a run-of-the-mill house type on-off switch.