Adam,
I think, given that my coach is a 1999 Marquis Tourmaline, we probably have "dead ringers" for vents. I know that initially I was frustrated with mine because of the thermostat, but found that if I want them to open and stay open unless it starts raining, I can use the switches to force them open.
I believe it does what you're wanting to do, ie it opens the vents and disables the thermostat from working.
When I command mine to open using the switches above the dining room table and on the right hand side of the bathroom vanity, they open, and they stay open unless it starts raining. It makes no difference what the thermostat is set to in this case. When I turn these switches off, they close (but in this position the thermostat takes over so they may not close depending on the thermostat setting).
I'll also point out that early morning can make it seem like the switches don't work when you command them to open and that's because of the dew that has triggered the rain sensor. I've caught myself, a couple times, wondering how both vents could simultaneously fail to open, then realized what was the matter.
I do wish mine had the reverser switch to draw air in. Right now if I want to draw air in with windows closed I turn one fan on, and that draws air down through the other.
Mike