It's a simple 12v appliance, just switched. Coming off the water pump you should see a red 12v wire and a black ground. I would try wiring it directly from a power source, perhaps the fuse panel which may be close by depending on your floor plan. If it doesn't come on and the fuse is good then the pump is toast. Not that big of a deal though, around $50 for most of them. It's a standard RV part you don't necessarily need to get from SMB, you can get a capable water pump from any RV sales/service/parts center. Make sure it's above freezing when you try it!
Currently vanless. Weird.