There are numerous posts on how to rehab these old Nicro vents. It sounds like the newer models don’t last very long and the older ones, especially with the stainless covers are more durable and worth restoring. I have 3 from the 1990s. One is located under a dodger and the other two are fully exposed. For the one under the dodger, I simply rewired it to a 1.5 volt solar panel just forward of the dodger and used the same battery holder that it came with. For the two that are fully exposed, the solar panels were shot, the battery leads corroded and battery holder broken. For each one, I removed the old panel using a heat gun, and installed a rectangular 1.5 volt solar panel by nesting it in a cut out sheet of polycarbonate plastic and covered it with a round piece of polycarbonate plastic, using silicone to seal it and make it water tight. I ran the battery wires into the cabin and connected them to battery boxes, one above the ceiling and one on a wall. Seems to be working great so far.