You're completely right and I'm just waiting for the epoxy to fail. I don't drive it yet so it's always at least within the neighborhood, the only place I drive with my dad to test it. I plan on using one of those switches you linked to before but I wanted to see if I could make the one I had work so the thing would just run for once. Nope, this switch is plastic and just has two wires coming out of it and when it reaches the switching temperature continuity occurs between those wires so I just wired it in series with the battery and relay.
Good news! I found the switch we used on the car that used to have the electric fan on it and it's installed and everything s working perfectly!
